First, you should seriously consider re-selling the Ultegra components on eBay, then you should look on CraigsList (http://www.craigslist.com) or eBay for a nice used road bike in your size.  Look for Trek, Giant, Miyata or Specialized. Stay away from classic '70's bikes as you don't want to do any restoring.  One of these bikes will give you thousands of miles of riding with no need for upgrading.

If your heart is set on improving your GMC, you should start with the wheels, they are the most important thing for the performance of a bike. You can find lots of used wheelsets on eBay, just make sure that they accept the same brand/type of cassette as your rear derailleur requires.

 Then, make sure you've got a very comfortable saddle.  After than, you should consider a brake upgrade as that's a safety issue.  If you aren't satisfied with the shifting, the derailleurs and shifters go next.  Last, should you consider a crank-set.

 Also, make sure that the bike is correctly fitted for you.  It doesn't matter how good the parts are, if the bike doesn't fit, you'll never ride well.

I bought a 2008 Felt F85, size 58 for around $1,000.00 and it is night & day between the 2 bikes.  Shimano 105's and Ultegra gruppo and a quality double butted aluminum 7005 frame.  My only upgrades were a comfortable seat (personal preference) and Continental Grand Prix 4 season tires.  I would stick with an entry level Felt or Trek and sell the Ultegra parts you have.

I considered upgrading my Trek 1000 (a fine ride) but couldn't justify the cost of upgrade parts compared to buying another bike.  I ended up finding a nice Scott CR1 full carbon bike with Mavic Aksium wheels with a blend of Dura-Ace and 105 components for $1000.  It is a world of difference.

Marten

ive been looking at the motobecane any thought on them

 Tim4706

I, myself, picked-up a bike at K-Mart for something like $119.00, and--against the advice of every bike shop owner that I spoke to--spent less than $300.00 on new, quality parts for it...you know...things like a Campy Crank and 52-42-30 chainrings, with a bottom bracket and pedals (for under a hundred clams), new shifters (thirty-five bucks). 

New hubs and tires only sets one back about $50.00 out of that $300.00, re-lacing the spokes and truing the wheels just isn't that big a deal, and dropping a 9S cassette onto the freehub is nothing...and adjustments don't cost you anything at all to make.

So, for something less than one-third of what all the experts told me that I would spend, I have a bike that is, admittedly, heavy; however, the frame doesn't flex and it's exactly what I wanted in terms of my ability to ride it.

I have a Specialized for the long rides, but my kick-about bike is geared identically, so I get the same work-out on either frame; but I'm not going to lose the same investment if somebody happens to nick my K-Mart bike at the grocery store.

I took the bike back to one dealer who was particularly adamant about my doing this, and asked him for his exact reasoning as to why the bicycle wouldn't work well for me, and why I should not have done that myself. 

After looking the bike over, he admitted that it would work just fine; but, in his opinion, I should not have spent "all that money" on a "generic" bike.  He said that I should have bought the bike that he had recommended to me months ago; which, he said, would have been cheaper. I then responded with what I paid for the parts, and showed him receipts when he expressed disbelief.

I kept pressing him for LOGICAL REASONS, and he simply could not come up with anything that had even one fact to back it up.  His fall-back was to simply get himself real angry.

There is room for an opposing opinion on this, but I don't see many people acknowledging that.

Now, to the OPs original queston:  Get over to www.BicycleTutor.com and visit Sheldon Brown's site (www.SheldonBrown.com), and you'll find more than enough information to take your project to the next step.  Also, pick up some bike repair books and applicable special tools over at Amazon.co.  These are a wise investment for any bicycle owner.

[EDIT]

Afterthought:  That K-Mart bike has, by the way, tripped-over the ODO at around 5400+ miles as of yesterday, and is just over a year old; which means that I'm tipping Sheldon Brown's published stats on department store bicycle miles ridden before landfill burial to something more than 75 miles average.  That, or there are a lot of bikes dying at mile 1 to compensate for me.

Second point, Since my wife calls me cheap, I say ride the denali till its wheels fall off, replace/upgrade what your comfortable with in your own workspace. spending shop dollars for upgrades, long term better spent on better bike. My quality arguement, I have a pair of Pearl Izumi shorts that are still in damn good shape after 5 years. My wife got a "store" brand and they are only 6 months old and look the same as mine.  I spent $70 when I got them, she spent $35, at this rate in 5 years she will have replaced and out spent me by far.

Upgrade and balance what you want, there your bikes and you ride them. We are all just giving forth, and sometimes we get stuck like the dealer trying to sell or upgrade cause we get snobby about it.

I've been upgrading my 14year old trek y frame MTB, cost a bomb back then and i love the frame. Figured it was time to replace the rims, they've had a hard life and were getting a litle skinny in the braking surface. Got some new rims, figured a disc upgrade would be nice, that meant a whole daisy chain of events that a lot of people wouldn't attempt but i've got a light strong and well loved frame i want to keep.

So significant dollars later I've nearly completed the upgrade, rims, brakes, shifters, forks, chain, cranks/chainrings, rear cassette. Needed forks for disc mounts, needed shifters because my old brake/shifter was combined and not hydraulic type, went to 9 speed with shifter coz 8spd hard to find, new 9spd cassette/chain wouldn't work with worn chainrings, hard to get canks without bottom bracket, couldn't get chainrings because they've changed from 5arm to 4 arm cranks...etc etc.

Upgrade at will, but keep in mind that new stuff is not always the same as old stuff (or cheap stuff) and might lead to a spiralling cost.

Mates said my upgrade was a can of worms. It is. But i've put a lot more life into the old girl and for the same dollars I wouldn't get anywhere near the level of gear or lightweight bike. Besides, I haven't spent any money on it for ages!

http://www.parktool.com/repair/