240 doors are easy to take apart. All you'll need are a couple of flat screwdrivers (large and tiny) and a phillips. Also, possibly a Torx screwdriver set if you come across late model cars in the junkyard.

I'll give you the disassembly for a complete, intact door. The doors you find could be missing some of the parts.

Unscrew the lock knob. Snap off the rectangular trim at the inside door release. Use a tiny screwdriver to remove the cover of the window crank. Unscrew the crank with the phillips. Remove the two plugs in the armrest/handle with the tiny screwdriver. Unscrew the armrest screws with the phillips (needs to be a long one for this). Rotate the armrest 90° until the back end points straight up. It should then unplug from the door socket. Remove the 3 clips for the door map pocket by turning 1/4 turn. Pull the map pocket up at each end to unclip from the pins. Tilt the bottom of it inward toward the car to release the center bracket. Unscrew the two pins that held it on. Take the large flat scrwedriver and work it around the perimeter of the door behind the panel, prying out each plastic clip as you get to it. Take your time, they're all a little fragile. (In the junkyard, grab a couple of these plastic rivets and extra screws, you always lose a few). The door panel is now free- pull away from the door and up at each end to unhook it at the top. Sneak it out from under the mirror handle- don't break the plastic trim there. Before taking it away, remove the speaker wires from the door speaker.
Now there's a plastic sheet in the door. remove that or fold it up and tape it out of your way with duct tape. Look at the way it hangs before you remove it- it's designed to channel any water leaks into the door bottom and away from the door panel. Take a picture at this point if you aren't sure.
The window clips to the regulator (winder) with a metal spring clip, and a plastic washer behind that. Remvoe the two clips at the window bottom after winding the window back down. WATCH YOUR FINGERS! YOu don't want to get pinched in the door. The window tilts forward and then you can wiggle it out of the door tracks. WIth your old window, you'll need to probably vacuum a lot of glass out of the door bottom. Also clear the window tracks of broken glass completely. The regulator assembly comes out with a few 10mm nuts and one more clip through the rear of the door. Inspect the plastic slide- a tuning-fork shaped piece of plastic that the one pin rides on. Put it back into the shape it was in when you removed it and take a picture if you think you'll have difficulty getting it back together. Take your time and be patient getting this thing out of the door. It seems bigger than the hole it's in but it will come out.
To quote Chiltons "Assembly is the reverse of the Above".
Good luck! You can do this job- I can tear down a 240 door in about 5 minutes and that just comes from practice.
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Rob Bareiss, New London CT ::: '87 244DL/M47- 221K, 88 744GLE- 202K, 91 244 181K, 88 244GL 145K