1988 300E w/ 23,000 miles

[JIMMY400]

May have a chance in a few months to buy an '88 300E with about 23K miles on it. Always garaged. Had a chance to get a brief look at it and cosmetically very sound, only some slight scratches on rubber part of bumper and a little spot of rust on outside part of fender which can be addressed. Original paint very good. Rear window did not work. Did not get a chance to drive but did rev up engine to about 5K and sounded smooth as silk. Also A/C came out very cold very quickly. Will be able to look at again end of summer.

Questions.
Any opinions as to price? (Has not yet been discussed)
What should I be aware of due to lack of mileage for a 23 year old car?
What would you have a mechanic do first with a car like this?
Any other thoughts/ opinions very welcome.
Thanks so much.