My 2 cents:
Great cars even though my head gasket just blew:-( I know I'd never find a better car for the price of a valve job, which I am going to have done.
About 2K but the motor will be like new.
Vacuum hoses and lines are important areas to look at as are breather hoses. Stiff, cracked hoses are a sure sign of neglect.
Replaced all of mine and it helped with running problems. Also, whatever MB you buy, change the fuses. Don't assume they are okay. They do wear out.