94 sl2 wierd shifting HELP!!!

I obtained a 94 sl2 from a friend the car runs great has some cosmetic flaws but the worst thing is the transmission. I was told that the clutch was replaced I believe this because it's very stiff. when in reverse you get full power but in any forward gear it feels spongy. Starting out in 1st feels like starting out in 2nd or 3rd. I know everything for this car is expensive but it's a strong running car. Any help would be appreciated.