Rattle/Clanking noise when clutch pedal not depressed

I just bought an 02' Forester 5 Speed (manual) with 131xxx miles on it. It runs fine but makes a really loud rattling/clanking noise that goes away only during deceleration and when I push the clutch pedal (the noise still remains while the engine is at idle, but it is quieter and a bit more intermittent). At first, I thought it was a rattling heat shield on the exhaust, but when I realized that it goes away every time I push in the clutch, I began to worry that it might be something a bit more serious. I've heard that this symptom could possibly be caused by a bad input shaft bearing on the transmission, but are there any other possibilities? Also, if it is the bearing, what on earth could cause it to go bad??? My biggest fear is that I'll go to all the effort to replace it, only to have the new one fail because I didn't fix the "real" underlying problem. If anyone has any knowledge to shoot at me about this, it would be awesome! Thanks!!!

It's porbably time for a new clutch kit.

I think you're right...gonna maybe pull the tranny out this week and see what I can find out. What I really wonder though is if it will do any damage to anything if I keep driving the vehicle for the next couple of days. It still drives good, just sounds horrible.