I did a refoam job a while ago on a 12" sub. It was not that hard, and it came out fine. Used a kit from Parts Express that supplied a new foam ring, special glue, plastic shim strips, and a new center cap. You have to cut the center cap to insert the shims around the voice coil so the cone stays centered with the foam removed. Then the foam is removed and replaced, and the new dust cap finishes it off after removing the centering shims. I don't know if there are any special considerations for your particular speaker, but I would recommend checking with the JL technical support dept for advice on parts to use-- maybe they have their own special kit.

Also, check youtube for instructional videos, there are probably some examples of speaker repair.

In your case, if the foam is not starting to dry up and fall apart, then regluing is a good first step. The glue that was in the kit was a white glue, and it said it was a specialized type, but you can probably find it separately by doing a little research. Check with local stereo shops for advice and see if they can supply the glue.