I think Magnecor has it about right, without the technical expertise and testing facilities you're wasting time, if you want extra protection put the PEX cover on your existing wires and keep a check for signs of attack .... but sounds like you'd be better off to get the garage built, if the rodents can't chew the plug wires [and they do gnaw on metal to keep the teeth from growing thru their lips], they'll gnaw on any other accessible wiring .... and get some traps out
Bill
