Having pulled 2 engines (300SD and 240D) with this mount system tells me that Junkman is right on target. (Of course, the 240D lacks the shocks). But yeah, clean the hex and tap in the socket before applying torque.

Not that you've rounded off the head (no, it's NOT stripped - that refers to a failure of the thread) the easiest thing is to buy yourself a 3/8" (say, 10ish mm) LEFT HAND drill bit. Chuck it in a reversible drill and, with the bit spinning what would normally be backwards, drill out the bolt. Sometimes you have to drill off the head but often the bit will catch and yank the bolt out. Left hand drill bits are the cat's - um - meow.

On the two I did you could get in there pretty well though you may need to pull the turbo on the passenger's (right) side. It isn't hard to do.

Dan