well, i tightened all but two valve cover bolts down with a torque wrench and wouldnt you know - the next to last one snapped. the bulk of the bolt is still inside the cylinder head, and the valve cover seems pretty tight and secure - it was the last bolt on the inside row of the driver's side valve cover (toward the firewall). i plan on putting some sealant in the little hole in the valve cover where the head of the bolt would be and hoping it doesnt leak any oil. ill be crossing my fingers. :\

I wouldn't worry about it too much. There shouldn't be any pressure in the valve covers or anything like that so one bolt shouldn't make a differance as long as the gasket is OK.

well, i started the car up with the missing bolt and no leaks there. what did happen was that oil was very slowly seeping out of some of the bolt holes, beneath the washers. i loosened each bolt about an 8th of a turn while the engine was running and it seemed to stop for now..