Mine had a trans leak where a connector to some kind of sensor was plugged in. I hear that's very common, they replaced the whole thing. The seat heaters are a not if but when problem. Check 'em out. Check out all the TSB's (technical service bulletins) on the forum and online. I don't know if your buying from a dealer or fast talking Joe, but my dealer had all the previous work done in the computer. Do a car fax check to make sure it wasn't crunched. Do a search on the forum for repairs or work done under warranty. A couple of the guys here had laundry lists that would shock you. It's a great car but you're right to do your homework, do a lot of it, these things can get real pricey when it comes to replacement parts. It is a Benz.

Sorry about the lousey punctuation but it's too late to proofread