ok, i'll try to answer that question - but i'm no ps3 pro
what about warranty??
if it's under warranty - let sony handle it.
depending on the age of the ps3, the overheating could be a dust problem, this dust can also burn into the lens of the laser - so cleaning it with a slightly wet microfibre cloth could help..
BUT:
the ps3 has a, design flaws that it couls easily overheat and b, the laser could be toast or c, the software has it's own will ;-)
another thing to try is a system restore, but i would try to adjust the motor/laser before that. (remove the disc from the ps3 and hold down the eject button for 12-15 seconds)
if everything fails - you will most probably need a new drive - and no, you can't use a regular bluray drive for that. the ps3 has a special optical drive - try a search on ebay ;-)