IPhone 4 mute switch, volume buttons and mic broken?

Simply put, I dropped my iPhone 4 about a month ago, and since then the mute switch, '+' volume button and the smaller microphone (at the top of the phone) don't work anymore. I took the phone apart to see if a wire was unplugged, but everything is fine internally. Is there something I can replace to fix this problem? It's annoying because I can't take videos with sound, etc. Thanks.

Added (1). I can fix the phone myself if I know what parts I need. I'd rather not go to a shop.

Go to a store called Dr. Phonez. They fix any phone. If there isn't one near you, go to the Apple store