codealarm system

i have bought a 1992 explorer that came without a alarm key fob. its a codealarm security system. i have found several of these key fobs on another site, for alot less than at the codealarm dealer, but what i need to know is can my mechanic reprogram this or does it have to go to the codealarm dealership....this means towing !!!
any info would be greatly appreciated thanks !!!