Frame slider?
 

My bike was wrecked when I first bought it, and I'm guessing this was a frame slider at some point? The other side has one in the exact same spot, but isn't damaged. Am I correct in assuming it is a frame slider? How bad is this? Any ideas on how I can go about fixing it?

Also, yes, I've replaced that awful, rusted clutch cable already lol

imgur: the simple image sharer

Looks like it.
Pair of vice grips to unscrew it and see if the new one fits. Kind of looks bent a little.

Is the housing around the bolt replaceable?

The black part around the bolt is part of the frame slider and I believe the sliver part is as well. Just unbolt the old one and the new should slip right into place.

looks like a slider, possibly used once or twice in the past ;)