OK, most likely it is not the regulator, they usually don't go bad. However, it may be the motor. Get a 12 or 14 volt cordless drill battery. Open the access panel on the tail gate. Find the motor leads on the left side just under the cutout access hole. Then follow the wire to the motor, along the way you will find a connector. Take it apart, and use a set of jumper leads to connect to the window motor. If it doesn't work, reverse the leads, (that is basically the same thing the switches do with the voltage). If the motor doesn't move then, the motor is probably bad. If it does move, you have a wiring problem.
Good luck,
In the diagram below the safety switch shown near the motor is often the cause of both switches failing. It is attached to the left side tail gate latch and not to easy to get at. If the motor works with the above procedure, try 1. pushing on the left side of the tail gate and operating the switch. If it works, you can do one of two things; adjust the lugs the latch grabs or bypass the switch. The function of the switch is to prevent you from closing the window if the tail gate is not closed. If you have your window half way up and close the tail gate :-& you will break the glass.