If you have an electronics parts house near (radio shack might have it) ask for solder rmover. It is a wire mesh that you lay on solder and heat, the solder wicks into the mesh and leaves the contact of the jack free, you just change the jack and resolder.
if they don't have the mesh (cheaper) they might sell solder remover tools that suck the solder out. They work great after you get used to them. You heat the solder then quickly stick the tip of the tool on and release the button and it sucks the solder out.
Finding the jack might be the problem, Radio shack or a parts house if not online.