Well I can definately understand your concern. Last thursday my mothers car had the head gasket fail (not a MB, but a 94 Ford Thunderbird). I started early sat morning and 11 hours later I was done replacing both head gaskets.
The car runs like a champ (just like when she was new just that it has 64,000 miles on it now). Its amazing on how fast it went. The only thing that led up to failure was that the car had a stumble every so often when idling on sunday, and then on thursday the gasket failed causing plumes of white smoke out the muffle. The car was never abused and we owned it from day one. Ford has extended to warranty on 94's and 95's V^ engines so this repair would have been covered, but I just don't trust anyone these days.
Hope all is well with you 300E....I'm going to be doing my 300CE next month to cure a slight oil leak from the front of the block.
1995 Jeep Wrangler
1995 Ford Thunderbird