Yeah, if the only problem is the 1/4" jack itself, that'll be no problem to replace. You should be able to (or at least one used to be able to a couple of years ago, I haven't looked recently) buy a replacement jack from Radio Shack. There's really nothing special about the jack itself.
The jack just fits into place from the inside, and that hex nut around the outside just tightens down with a pair of pliers to tighten the jack to the chassis.
Of course, before you fit the jack to the chassis, you'll have to solder the leads from the circuitry to the jack leads. Depending on the construction style, there will either be wires connecting the circuitry to the jack (the easiest to work with) or there may be rigid metal conductors. The rigid conductors can be trickier to work with, but you can just either connect them or replace them with sheilded solid core (typically not stranded) wire.
This is, of course assuming that only the jack itself needs replacing. If there is more internal damage to that circuit, that's another story altogether.
HTH,
G.