These notes are intended to help someone else who may be doing this (or a similar) project. If you need to paint your doors, you'll need to fully dismantle them to do it right. You also may need to make a few modifications to make the doors work for your application.
You'll need a basic set of metric tools to do this job. In addition to those, here are a few of the more-odd things you'll need. Other parts/tools are listed in the appropriate sections below, which may or may not pertain to your application.
1) Remove the door handle and lock escutcheons, and the window regulator handle. For removing the window handle, use the trim tool (or a screwdriver) between the large washer and the handle, prying the washer and card back from the handle. This will expose a small clip - remove it and the handle will pop off.
2) Remove the door card using the trim removal tool. It is attached with a variety of fir tree fittings around the edges. Two corners have different fasteners... these came off quickly with the trim tool as well.
3) Remove the two clips that secured the door handle to the frame - these also hold the insulation to the frame. Next, using a fine knife, cut the adhesive that secures the insulation to the metal. Use care not to tear the insulation.
4) Unhook the exterior door handle rod from the latch mechanism. Do not unscrew the handle itself. Remove the interior lock.
5) Roll the window down far enough to unbolt the glass from the regulator assembly, then push the glass back up and away from the regulator.
6) Remove the machine screws around the perimeter of the regulator assembly - these secure the big black frame to the rest of door. Once removed, the entire assembly should separate from the frame, along with the door handle. Some portions may be secured with more of that black adhesive that you cut through earlier - be sure you didn't forget a linkage rod when you start tugging...
7) Using a Phillips head screwdriver, remove the two screws that secure the window track to the door frame at the base. At this point, you should be able to move the glass back down, then twist the track slightly to allow the glass to escape the track and be completely removed.
8) Remove the rubber/felt liners at the sill. Use care not to bend them.
9) On the inner side of the exterior handle, unclip the lock and latch rods, then remove the handle from the door. Leave the latch attached to the door.
10) Use your screwdriver to hunt down and remove the remaining handful of screws that secure the rest of the glass track to the door.
11) Remove the rear door track, which should slide out if you've removed all of the screws. The plastic edging in which the track sits should then pop out as well.
12) Remove the front track and backing, then the top track and backing. Use care not to bend the tracks when removing.
13) Remove the plastic covering the latch, then unscrew the latch from the door.
14) Remove the rivets securing the weatherstripping to the bottom of the door. You can clip them off from inside the door, drill them out like regular rivets, and/or hack them off with a Dremel. I used standard 5/32" (4mm) aluminum rivets for reassembly.
You now have a hunk of aluminum in the shape of a Defender door.
You can re-key your door tumblers to work with your ignition key. You can do this fairly easily too! It took me about 20 minutes to get it perfect the first time, then the second one was leagues faster. See this page for information.
I was able to get VERY close after using all of my wafers. File the wafers along the bottom to fine-tune them (they're soft brass).
Reassemble in reverse order, but stop before installing the insulation, then do the rest once it's on the vehicle - this will allow you to make any necessary adjustments to the linkage before sealing it up. Also, you'll need the door card off to put a wrench on the hinge bolt nuts.
If you want to mount the speakers in the doors like the NAS 90 SW setup, get two of Land Rover part #STC3312 (6.5" speaker spacer/bracket contoured for the SW door card) and use a 4 3/4" hole saw to cut a hole in the card.
You'll also need to adapt the wire flex tubes for use with the SW doors - just drill another hole in the side of the card to accept the flex tube.
If you're coming from a ST D90, you'll need SW striker pins and plates, as the anti-burst strikers will not work with SW door latches. Part numbers are at the top.
If you have the old rusty hinges, now is the perfect time to install new ones that won't rust up as badly. If you're using new Genuine bolts, note that they won't work with the old captive nuts (different thread)... either replace the captive nuts in the same clips or get eight new clips (part #BYH500100). The genuine bolts also have a T-40 Torx drive head as opposed to the PoziDriv - given the torque needed to properly secure the doors, you'll probably want to use a socket/ratchet.
If you have a 1994 model Defender, you have a bonus step: you'll need to upgrade your door checks. Note that the 1994 checks hinge on the bulkhead and slide into the door - a setup that will not work with SW doors. You'll need to scrap those check and install 1995+ MY check assemblies, which hinge on the door and slide along the bulkhead. There are a handful of parts required, but the end result is a nice improvement: they actually hold the doors open! You'll also need an metric riv-nut riveter and a suitable riv-nut if you wish to secure the RH bracket's (assumiung your Defender is left-hand drive) third bolt to the bulkhead. M6-1.0 matches the other bolts.