I bought my 2005 645 vert in 2010 for 27k with 78,000 miles and a cpo. I too was a little nervous but the car was in immaculate condition and it had 22k or 8 months to go on the cpo plus it was love at first sight!! Here is a list of things I have had done so far: Th Front brakes (covered by cpo just before it expired) battery $89 ( installed at Sams Club vs $500 or so at the dealer and after 2 years no problems) Thermostat $325 (Indy), spark plugs $290 (Indy) front thrust arm joints $600 (Indy), Rear brake pads $225 (Indy). Except for the battery and brakes, the other items were replaced around 100k miles.
I am taking the car in next week to get the rear thrust arm joints replaced as well as the O2 sensor. Find a good Indy shop and you will save LOTS of money vs the Dealer. These items are normal wear and tear stuff that I was expecting to have to do. The engine runs strong and I love her just like the first time I drove her!! The only thing that drives me nuts is the damn convertible top gets stuck every now and then but thanks to the BOSEMAN10 PUSH, I haven't had to take it in to get fixed.
Hope this helps in your decision, I have no regrets!!.