I had to replace my passenger side window motor/regulator assembly about a month ago ($167). Wasn't hard to replace at all. First thing I would do is get a factory shop manual for your truck. It's already got a troubleshooting list for this very problem. I don't have my manual in front of me so I'll go by memory.
#1: Pull your passenger side door panel off. Be careful when you are pulling the plastic inserts out. There is a special tool made for this, I didn't use one though. I took a brake adjusting tool and a gasket scraper and pried on either side off the insert and they came right out. I was able to reuse the inserts too.
#2: Pull your window switch assembly out of the door. Turn your ignition on and check for power at the input terminals. If OK check for power at the output terminals with the switch turned on (you can also check the switch without power by verifying continuity between terminals based on the switch position, It's explained in the manual).
#3: At this point you will either determined the switch is bad or the motor is getting juice but not moving. It may be the motor is bad but it also may be that the window is binding in it's track. So next unbolt the regulator arms from the window and verify the window will move freely in it's track. Most likely it will be your motor that's bad. The motor/regulator is only sold as an assembly by the dealer. I found remanufactured motors online (I think the best price was carparts.com) but I really wanted to fix my truck that day. My window had died in the open position (nothing like driving around with duct tape holding your window up).
Hope this helps,
Mike