I've got a problem with my powerbook pismo. I noticed that it would be very hot to the touch on the bottom of the case, especially when watching DVD's or runnning other intensive programs. The major suspect is the fan, so I am going to replace it, probably with one from eBay. But on ebay, 9 times out of 10 the description says "pulled from a working unit so it SHOULD work." So, my question is, how common is it for these fans to fail?