I have purchased a nice 01 3500 2wd dually. I got a plain key with it and no key fob. I asked about a keyless entry system at my local dealership and the parts person asked if it may already have a module in it . Having power door locks from the factory they said it was possible to already have this module and it was about a hundred or so cheaper to buy key fobs and prgram them versus purchasing a keyless entry kit for $178. 00. MY question is,where is this module located?