That's the same year as my OCR2. The OCR1 was about 1K new as mentioned above and weighs, as you found, about 23 lbs. ( I knocked off weight on mine with some Williams' 30's). It's not a bad price...it's not a great price. If it's clean and not worn out, then why not? The 105 is an excellent group so no worries. Hey, I'm still running my rear 105 and Tiagra FD just fine.

Mostly, if you like the bike and it fits well, then I say go for it. Try not to get too caught up in chasing other stuff down. Besides you get a little deal with the trade in which is unusual....most shops aren't going to do that for you. And you won't get that with a private party so in a sense, that's free money.