Five hours does seem a bit steep. Is he running over to Betty's for lunch?
There is no big mystery to adjusting the valves on a 16v. You just have to measure carefully and juggle the shims around for the various thickness's needed. You will probably have to buy 1 -3 shims from the dealer. If you can handle a BMW adjustment, the Benz is just a bit more work since the cams need to come out. Just loosen the cam keepers evenly and slowly and install the same way.
I would worry more about the tensioner. If the chain is rattleing at start up, it could have slapping the chain guides and broken them. The top one is easy to replace, the bottom one is a !@#% and takes a LOT of work (at least several hours to just get the front cover off) to get at.