Here's the FSS schedule for a 2001/2002.
I highly recommend you have whatever you buy inspected at a dealer. They'll be able to tell you what needs work. For example, you'll be very happy if you know it needs front rotors BEFORE you buy the car.
The normal wear items to watch for at this stage will include:
- Both motor mounts
- Trans mount
- Brake light switch
- Possibly the differential side seals
- Flex dics
- Possibly the catalytic converters
The cats can be the most expensive item. They need to be replaced when the ceramic cores separate from the metal shells. You can tell they're bad when they rattle just off idle.
The spark plugs should have been changed by now. If not, I’d deduct that from the sales price. The transmission fluid should be changed as well (about $300 at my local dealer).
Not so normal, but common wear items are the power seat motors. If you’re handy, each motor will take about an hour and cost about $130 at the dealer. If you’re not handy the dealer will probably bill a couple of hours labor on top of the part.
Lastly, you may want to consider joining the Mercedes Benz Club of America. The parts and service discounts are more than enough to cover the yearly membership.