At that milage I would hope and pray the timing chain/rails have replaced along with the valve stem seals. The top ends of these things seem to be the weak link, if you want to call it that-- including worn cams, bad rocker arms etc.

It certainly could be money, pit: A/C work is $$, top end as mentioned, chain/rails. Looking at a few thousand right there.

Transmission is another issue, $1500+ for a rebuild, see:
http://www.peachparts.com/shopforum/showthread.php?threadid=44423&highlight=transmission+piston

If you get serious have a qualified MB tech perform a PPI.

Let us know that the seller says!