The driver's side vent window seal on my 1985 W350 was leaking so when I decided to replace it I took some pics and notes. This should be the same procedure for any Dodge Ram truck or Ramcharger 1981-1993.
You will need:
A pair of Vent window seals Part #vwk 3110 78
Torx bit driver #25
Flat head screwdriver
First thing is to remove the door panel, its held on with 3 screws, one torx screw on the window crank and one 7/16" bolt on the door handle.
Pry the panel off.
Remove the window glide seals, the lower two are held in place with metal clips.
The vent widow assembly is held in place on the top with a screw on the upper outside of the door frame and on the bottom by a bolt. There is an access hole for the lower bolt above the cutout for the speaker.
Once the fasteners are removed tilt the assembly back and up to remove it from the door frame.
Now that the assembly is out remove the old seal and vent glass from the frame.
Insert the new seal and then do everything else in reverse order.
The seals cost about $50 for the pair and it took about an hour for one side. There's also a good video at 1A Auto.