to "be prepared", i'd just get a replacement jack assy or two from line 6.
like i said, you have to take the whole beltpack apart to get to the jack, but once you do, the complete jack assy just pops out to be replaced.
watch out, because there's several tiny screws and a couple little spacers that all have to go back on just right, as well as the buttons and various little parts that can fall out when it's opened up. (this thing is not really "user-serviceable" unless you're pretty skilled.)
the stock jack is attached to a little circuit card, which has the spring contacts to get to the rest of the guts. to install the metal jack (a switchcraft "TB4M",
Invalid Link Removed), i had to de-solder the original from its little card, then run 4 tiny flying leads from the new jack,
through the mounting hole in the transmitter, and finally to the solder points on the card.
i also had to
ahead of time get an extra hex nut (like the one from the old jack) and grind it down to a square shape so it would fit inside the beltpack hole and serve to thread into the new jack to hold it in place. (the old one threaded from the front while the new one threads from the back.)
so it's:
take apart beltpack
pull old jack assy and its little card
de-solder jack from card (an absolute bitch without a solder-sucker, liquid flux and de-soldering braid)
grind down leading edge of the little card so new jack will clear it
solder 4 thin leads in card, maybe 1 1/2" long
modify nut to fit just inside hole in beltpack
feed the 4 wires
through that nut and out the hole in beltpack
thread the included nut for the new jack onto said jack, to space it out so it clears the guts in the beltpack
solder the 4 wires to the new jack (i used a bit of ribbon cable with 4 different color wires, so i could keep track of what went where)
screw new jack into hole, threading it into that squared-out nut (i plugged a cable-end into the jack to give me a handle to turn it), letting the circuit card on the other end of the wires spin freely so the wires don't twist up
re-seat card in its little slot, tucking wires around it to clear everything
re-assemble beltpack
cross fingers and test unit
...
i shoulda took pictures, 'cause i'm not about to take it apart again!