There are numerous things that result in the symptom, "my tailgate window won't go up/down". You need to do some basic trouble shooting rather than shotgun parts replacement, that's too expensive.
Remove the access panel and jumper the motor leads to see if the motor will actually function. Reversing the jumper to the motor leads will make the motor go in the opposite direction.
If it doesn't work then you know what to do next. If it does, you still have some trouble shooting to do. I am attaching the wiring digram for the circuit. You will note that there are two fuses involved. One when the driver switch is used and one when the tail gate switch is used. Also the switch that is not being operated must be in the center position or the other switch will not work.
Get a volt meter and check it out. There are three connectors, one behind the left tail light, one on the rear crossmember left side, and on the lower side oo the left hand dash panel. The rear ones are often corroded even to the point that a wire breaks off. The tail gate safety switch in the left hand latch is also a problem if the tail gate isn't closed tight, (You might want to try putting pressure on that side and see if the motor works).
Good luck,
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