I did it to my 817, which is a bit different with the Sprag clutch, but I think the main case is about the same.
It's heavy....hope you have a truck transmission jack and note that the jack with the TC on it, does not fit to roll it out from under the truck. The front of the truck needs to be up a bit with very solid blocking. I think I needed about 8".
Keep notes and have a parts breakdown readily available. I misplaced a retaining ring and had to re-split it 3 times. Don't do that.
You will have to reset all three shaft pre-loads. I did mine by feel but there are sophisticated instructions that professionals follow. I prefer a light but firm pre-load so when it heats up from use, has room to expand without getting too tight. But I'm getting ahead.
I don't have experience with the section that shifts it in and out of front drive, mine had the over-run clutch. But I think most of it will be obvious. After the front engagement part is removed and the flanges pulled (mine slid off by hand), lay it on the side. Disassembly and reassembly are done that way.
Part of the fun is taking the old gasket off. Have a sharp tool. Keep all parts clean. Inspect the bearings and gears for wear after cleaning. Have new input and output seals ready. I doubt that you will find a pre-made case seal, but maybe you can. I used Aircraft Form-a-Gasket...and it was a good thing I did, since I had to take mine apart 2 more times.
The plates at the end of each shaft should be left loose when you re-assemble. They push on the race of a tapered bearing that when pushed in, tighten the bearing(s). One side is fixed, the other can be shimmed. Don't install shims until your ready for the final adjustment after it's all back together, leave the shafts (somewhat) loose. All parts can be freely rotated, high and low can be shifted. I used a little white lithium grease on my re-assembly, just to be sure there was some lube on startup.
Because there is no gasket, the cases may be slightly closer together than before and require maybe one less shim. I started on the input shaft and pushed the bearing race in with a screwdriver to snug, then put the cover on. It was a trial and error time, putting shims in (and removing). Here is the kicker for mine...the TC was new but had apparently never had bearings properly set, allowing movement and bad noise (would have self destructed). If I had known the problem to start, I could have done this in the vehicle. Live and learn.
Once you feel the difference in how the shaft you are working on turns, it will be obvious when it is getting too tight. Back down one thin shim. Then when you move to the next (intermediate shaft), you can "feel" it and tighten accordingly. You should have an extra shim or two from the case coming closer together, but it's possible you will have to make some. Move to the output shaft after the other two are set. Everything should turn freely by hand, snug but not tight and shift from low to high. Some gear backlash will be felt, which is easily identifiable from lose or over-tight bearings.
Re-assemble the front drive engagement (mine is different than yours).
I don't recall it taking any special tools.
Hope my description of my experience helps. Good luck.
