Spent the better part of this afternoon taking apart my bike and putting it back together. My barely-competition-worthy Trek Pilot now has a full Ultegra drivetrain! It was an intensely, satisfyingly educational experience, worthy of reduction to a bullet list of insights:

• Ebay really can save you money. Total cost of a “complete” Ultegra double/nine speed group: up to $900. Total spent bidding for individual components over about three months, including additional parts purchased at the local bike shop: $450.
• Buying things a piece at a time on Ebay is tricky. For instance, if you purchase your crank set separately from your bottom bracket, the bolts needed to connect them are probably going to be included with neither.
• Living near a bike shop is vital. I made three different trips to a shop barely a mile away — once for the aforementioned bolts, once for spacers necessary to make my new nine-speed cassette fit where my old eight-speed one had gone, and once to remove an impossibly well-stuck-on old bottom bracket. Really, it would’ve been better if they were just across the street.
• Tools matter. Using the bottom bracket socket wrench attachment in my “everything you need” bike toolkit, I spent half an hour grunting and pulling on my old bottom bracket, to no obvious effect. When I took it in to the bike shop, the mechanic had it off in thirty seconds using a dedicated bottom bracket tool with a proper integrated handle.
• Fixing a bike boils down to using an Allen wrench repeatedly. Which is to say, given the right references (I used Zinn and the Art of Road Bike Maintenance and some strategic Google searching), even installing new brake/shift levers was pretty easy.
• Knowing the right people is also vital. When everything was bolted on and connected up, I couldn’t get my derailleurs tuned. That could’ve meant a days-long wait till the bike shop had time to take the job, but serendipitously, I got an IM from a fellow cycling club member with more mechanical chops just as I was giving up. I took the bike to his place, and between the two of us we had it operational in half an hour.
• Learning by doing works. I’m not going to claim expertise after this, but I’m now that much less likely to throw up my hands and run to the shop the next time there’s a problem with the bike.

All in all: not a bad way to spend a Sunday. Shakedown ride is tomorrow morning.