On my brand new to me Trek 7500 I noticed the plastic ferrule that maybe screws into the bracket of the right hand (rear) shifter is broken. About 1/3 of the cable is broken/exposed but the rest seems to be secure. In taking the bike out around the block there was some clanking in shifting, I wonder if this broken part could be the problem or it is more likely my not understanding how to shift properly.

Is this a DIY fix job and if so, could I get some instructions here for fixing it?

Well, also, does it actualy need to be fixed, considering I only paid $110 for the bike and it might not get ridden all that far or that much, maybe I should just wait and see?