Just replaced the driver's side window in my '74 this weekend (gotta love the neighbor kids.)
Remove the door panel. Remove all the misc bolts you can find (4 around the window crank **may want to wait until you have the vent out but I didn't and I could have used another hand to hold onto everything **, 3 on the door handle (not necessary I believe, but they were there and I removed them and it worked), 2 in the lower front by the vent window, and 2 in the rear of the door that hold the rear track inside the door.)
Remove the top trim with 2 phillips screws on the rear of the door (this was on a '74 so may vary.) Remove all the screws along the top of the door frame around the vent. There should be 4 total: 1 holding the rubber piece and 3 around the door frame.
Roll down the window (I went it all the way down). Grab the vent window and you should be able to pull it out of the door frame. If it doesn't come easy, make sure you have all the screws out. When the vent pops loose, you should be able to turn it 90 degrees (vent toward the truck) and work it out the front of the glass. At some point work the rear track loose, easiest if the window is up. Then pull the bolts on the window crank and work the window and track off of the rollers. It's hard to explain how, but if EVERYTHING is loose, you should be able to worry the two wheels out. I had better luck getting the back out first and then doing the front. Might have to crank the window up and down to find where it's easiest for you. I'm sure that someone can tell you exactly where to put the window and have it work easiest, but that wouldn't be me.
After that, pull the window out and then worry out the regulator assembly. VOILA. One empty door.
Good luck and it's not too horrible. Take about 20-30 minutes if you're learning. Hardest part is getting the track off of the regulator but once you've seen it, you'll have an easy job of it next time.
