Keyless Entry Questions

[PineAppleExpres]

Ok I got a '99 Full Size C-30. crew cab automatic. The keyess entry range is pathetic. It takes multiple times to get any action with in 5 feet, its intermittant standing at the tail gate. I have already changed the remote battery so that is not it. I was wondering what aftermarket system that wont cost as much as a arm and a leg. I do not have a need for a complete alarm system. I would also like it to possibility take the place of the stock controller. Almost like a plug and play. I know I'm asking for a lot but any thoughts. Also where is the factory stock box is located so I can start point. So here I am with a pair of wire cutters in hand and frustrated.

Thanks
PAE