Re-solder/replace power connector with cold solder joint?

USB port/power connector moves up and down when I attach the power adapter and can no longer make a connection no matter what cable I use, so I suspect a cold solder joint, likely from the phone being dropped too many times with the cord attached. If that's what it is, I've re-soldered electronics (not phones) in the past to fix this, but I'm wondering: (1) Is that likely what it is or could something else be loose on the G7? (2) Has anybody ever fixed this issue? (3) How difficult would this be?