There's also a problem with the early head design which leads to a failure in the head gasket between the #1 cylinder and an oil journal between the #1 cylinder and the timing chain area. Could very well be that all you need is a new head gasket. The real fix is a new head but a new gasket will hold for a while.

This pic from the DaveM/gsxr collection shows the change in oil passage design -

http://www.meimann.com/images/mercedes/head_gasket/heads-both-front.jpg

Sixto
95 S420
87 300SDL