Keyless Entry Problems

I have a 2007 G6 Standard model, and the dealer installed an aftermarket remote entry system, Marksman, no remote start, no security system, the car is outside of warranty, and the aftermarket system is malfunctioning, it unlocks after 2 hrs, and then doesnt lock up again. Does anyone know how to fix this, I have a feeling that I need to take it someplace, but since I have moved away from the dealer that I got it from, about 1500 miles, and my local dealer told me they wont touch my car.

Does anyone know where they would have put the box for the keyless entry system? How do you get to it, I have some reasonable mechanical skills, just not with cars, and I think that I could replace the box if I could find it.

I found a retailer for Marksman in my new area, and will be contacting them to resolve the problem, but I fear they will charge me some ridiculous service charge to "figure" out what is wrong just to tell me that they need to replace everything and charge me for that too.

Where is a good place to get keyless entry systems installed, in central NJ? Does SEARS install them?

Thanks,