If it makes a noise when you step on the clutch, it's the throwout bearing.
If it slips, it's the clutch plate/pressure plate.
You don't describe the noise, so I am just guessing. Being 15 years old though, it's probably tired.
Any time work is done on a clutch, it is wise to replace all 3 parts referred to above.
You need to call several transmission shops in your area to get a price estimate on replacing those parts.
