I just purchased an extended warranty from the MB dealer for my 98 C230. This particular warranty effectively extends the factory warranty as to coverage. ( exclusionary type with a shorter than average list of things excluded, with no deductible, covers wear and tear, and is cancellable and transferable) It had to be purchased while there was still 30 days left on the factory warranty. the price was pretty close to aftermarket warranties. (Actually, service contracts).
There are some good background reading sites
Some of the warranties may not cover head gaskets - you have to really read over the fine print of what is included (or on exclusionary contracts, what isn't covered). Good luck.
2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)
Click to see 87 300E