First slide the ashtray/cigarette lighter out and there are 2 screws that hold the ashtray mount in place. Remove these and pull the whole ashtray assembly out, there is a plug in the back that needs to be unplugged after you remove the ashtray. Those are the only screws that have to be removed. The dash trim is mostly held in place with metal clips that just pop out. The way I did it was I slid a putty knife around behind the dash trim until I felt a clip. Then I lightly pried and carefully tugged on the trim and the clips come right out. Just do it slowly and one section at a time so you don't break the plastic. Now that the trim is off unplug the 4x4 connection (if 4x4) and if the trucks an auto shift it into 1st and just lift the trim out of the way.
I don't know for sure that a new headunit will fix your problem but I think it probably would.
Edit: Just thought I should add that you need a special tool to remove the radio. It's just like 2 U-shaped tools that release the clips that hold the radio in place. I was able to get the radio out using clothes hangers but looking back it would have been easier to just buy the tools.