Clutch not catching? Help please.

I recently bought a 2000 legacy B4 with TT. Manual of course and by recently i mean two days ago. I'm new to the Subaru world but caught the bug and already have major plans for this little girl. Today after a long gruesome day at the shop i come home and start her up. I notice the clutch has a lot of give and isn't firm at all. When i start out it revs for awhile and i give it a tad more gas until i'm around 4500 rpms and it starts rolling. No matter how much gas i give it, it won't take and it won't go over 30 kph. No matter the gear.. Oh and it almost rolls backwards trying to go up hills. It feels to me (a total nub but not a dumbass) that the clutch isn't exactly catching. I had a few friends look at and in attempts of keeping my hopes up they mentioned it could be the throttle position sensor and or the axle glove tearing (I'm not to sure with the terminology here) could have came lose and just barely pulled the transmission. He said this makes sense because of the thunking that would happen when slowly turning. Also the previous owner decided to tell me today that he blew out a transmission of his last Subaru about a year ago and he hasn't messed around with the tranny oil the last years he's had this one.

Thanks for the help! There should be an award of blowing a clutch out the first day of owning it.. It's sitting in the garage waiting to get the clutch replaced now though. I really wish i could have done it myself but i wouldn't know where to begin! But now i can justify to the wife that a WRX flywheel/ACT clutch kit combo is worth it so all is well.