SUCKS! I had to change the whole head because it cracked. Apparently a problem with the 5's, if the temp reads red chances are you cracked, or at least warped the head. My mechanic told me three minutes in the red, it's over. It has something to do with the length of the cylinder head in the staight six.
Take it somewhere that deals specifically with BMW's. Someone reputable, who's going to offer you a gauranty on work and so on. Chances are, if you have to come out of pocket, the delarship is going to rape you.
How do you know it's the gasket anyway? All you say is the oil stinks. Anyway, if you suspect head gasket failure don't drive the car until you have it sorted out.
Good luck. It's an expensive job no matter what.