m3 clutch

my friend recently let my friend drive my car and he went up hill. He came back and i smelt clutch... i drove it and i smelt clutch the whole time driving it for an hour...and then my clutch started slipping....you guys think i got a burnt clutch???? i then looked at the tranmission fluid and it was low...can it be that i just have a leaking tranny fuid or do i just have a burnt clkutch and i have to replace it???
thanks this is really important