Re: Spider, what to buy.
There's a buyers guide on the front of this forum, which you should probably read (it's full of good, valid advice). It will let you get a feel for if the car is in good condition. Also, check Parkers for a guide price.
I bought a 2001 2.0 Spider Lusso with 52K on the clock a few months back for £6500 (non alfa dealer forecourt in Leeds), and the first thing I did was spuff £850 on getting the major 60K service done. Also, the garage said they'd let me know if there were any problems with the car so the original dealer would be eligible to pay for repairs under the 30 day warranty.
You won't have this luxury, so one idea is to ask him to get the service done by a recommended garage, whilst also checking the car for other potential problems. If nothing comes up, agree to buy the car at recommended price and also cover the cost of the service (so he doesn't lose out). If the garage reports lots of serious issues then either walk away or negotiate a cost with your buddy that allows compensates for you getting the work done.
Just an idea anyway! I hope that the car checks out, they're amazing fun to drive and you'll have a great summer with it!
P.S - I think the Lusso is the model with leather seats and electric hood. Don't quote me on that though.