locks are VERY easy to rebuild as long as you don't mix up the tumblers. mine were all sticking and I pulled them apart for a build and lube. For the door, all you're gonna need to do is take the little silver cover off (2 small tabs) and then take the plastic glow ring and the small silver plate off, there's you're "trap door" or "flapper door" or whatever the hell you wanna call it. Small spring inside to keep it closed. make sure everything is good, maybe sand her a lil bit (just to clean it up) check and make sure the spring is good (I use pliers and bend the tabs out a bit so it'll stay closed) then put it back all together, and throw some lube in there too, I think there might be a special kind to use, mine was a thick white goo (hahaha). When you put the flat silver plate back on with the rectangle hole in it, be VERY CAREFUL, it will go on 2 ways, if you put it on wrong you'll have to angle the key to get it in, and it can be a major PITA.
oh, you probably bent the damn door, or it came out of the "hinges"...or some ass hole jabbed something in there