Head Gasket Leak

I have a considerably large oil consumption/leak rate. My mechanic, who was recommended as a very experienced MB technician, identified a leak at the rear of the head gasket. He informed me that the replacement is a 30-40 hour job because after removing the head, the bolt holes in the aluminum block usually have to be re-drilled and tapped. He estimated the work at $5000+. He said that some people try retorquing the head bolts, but if he tried it, you run the risk of stripping any of the aluminim threads and will have to then re-drill and tap anyway.

This sounds like an expensive job. Are there any alternatives? Or any proven ways to replace the head gaskets without having to re-drill and tap the holes? I read some postings about high temperature sealants which I see no loss in trying before I gamble next with a re-torquing.