Quetions..... 1988 300E

OK so I have been shopping for a new (to me) car for a little while, and today I found a 1988 Mercedes 300E. It has 150XXX miles on it and It is in pretty good condition. Can anyone tell me how long they last about how many miles one could put on it price of repair and parts etc. I would REALLY appreciate it CAUSE I WANT THIS CAR!!!!!!!!!!!!