Playstation 3 is notorious for over heating to the point its prossesing chip disconnects from its mother board.
Are you sure you aren't thinking of the XBox 360?
I have a 3rd generation 80g PS3 (model just before the slim) and have no issues overheating even after playing 6+ hours
Anyhow, they sell 3rd party coolers that are less intrusive than opening up the PS3. You may want to try one of them first.