You can change it yourself. They are typically pried apart with a screw driver. If my memory serves me correctly, there is a CR2025 battery in there (GM remotes until 2005...). Check before you buy a replacement, though.
As a public service to BITOG, I just pried apart the remote for my '04 GMC (I'll bet it's similar to yours). I just used a dime inserted in the little slot on the side of the remote, and twisted. Popped open like one of those plastic easter eggs.
OEM battery is a CR2032 3 volt. You can get batteries at Radio Shack or any well stocked hardware store. Replace the battery and snap her back together. Take ya 2 minutes tops.
As stated, battery change is simple enough, and certainly worth a try before going in for replacement. Just about bet it'll be the pick-up dohicky in the vehicle though. Those are dealer only and must be programed by them when installed (expensive). ,,,,,,,,,Did I mention expensive?
Just a warning replacing the battery may not fix your problem if it is having to push hard or multiply times. From what I can figure it happens becuase the little black pad oxidize which stops them from completing a circuit. I have had some luck fixing this problem in my brothers remote by sanding the pad with some fine grit sandpaper and wiping just a little bit of dielectric grease on the pad, just enough to get them shiny looking.
