I changed my valve cover gasket yesterday afternoon. I was nervous at first but I can't believe how straight forward it was. BMW does such an amazing job engineering these engines, its almost as it they designed them with us in mind. I was also pleasantly surprised of how clean it was. I just scrubbed the inside of the cover with degreaser.
I just took it for a drive at 430 this morning and no leaks.

One word of advice though, be very careful when taking off the cover. The rubber seal turns to brittle plastic and pieces can fly everywhere. I had to fish a small piece that I nearly lost deep inside the crevices of the engine .

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'03 Black BMW E53 3.0i 110,000+ miles
'03 Black Mercedes-Benz W211 125,000+ miles
'13 White Mercedes-Benz W2o4 New