My $.02 advice would be to get a good and reputable mechanic to go over the car for you pre-sale. I made a biiig mistake by buying a MB without anyone looking her over. Luckily I got out of that one and into a much more reliable car!!
The mechanic I use took 20-30 minutes and did some cursory checks of the systems (drivetrain, a/c, electronics, etc.), listened for undesirable sounds and looked for wear on parts/components that shouldn't be worn or, if they are, how much it'll be to fix.
You can also take the car to a MB dealer near you and, for about $90-150, they'll check out the car as well. I can't say if this is generally a good or bad move personally. I chose an independent.
In my case, I needed a new a/c blower so I had my mechanic give me a quick quote on it and I had the price reduced to compensate for that.
Good luck to you.
1988 300E 90k miles