yes, you can get the factory code yourself.... but you must remove the back seat in order to get it. if your not familiar with how to do that, so a search for "rear seat removal".... there are a couple good posts whth pics too...
when you get the rear seat back rest out, you will have to pull out on the "lining" material they use.
you will find a sticker with the 5 digit code. the sticker is stuck to a control module of some sort on the driver side of the rear cab wall.....
once you know the factory code, then you can reset your own custom code.. the instructions are in the owners manual.