The joint is covered in TM 9-1803B (it covers all three used by the jeep during the war), so it's not overly difficult to work on these …. with patience.
What goes into the knuckle? This is a question that repeatedly comes up on the G503.com. I'm not sure we agree on the answer.
The manual and the lubrication guide says to use CG Grease. This is grease, general purpose either. 1 for temps over 32F or No. 0 for temps below 32F. This is more or less the same grease you would use for your wheel bearings (except that calls for No. 2 grease).
I have the Rzeppa knuckles and these are not all that difficult to take apart and clean and then put back together (although it is a puzzle and I would not want to have to do this blindfolded).
When you take apart the knuckle do not reuse the old seal. They are not that expensive and it is reliably easy to install.
Now there are others that would have you put a liquid or semi-liquid in the axles. I'm not sure why. Putting grease in and on the knuckles have never left them "dry" in the 26 years I've had my jeep … and I have taken the axle apart way too many times. These folks swear by "knuckle pudding", you just mix up some grease and some oil, blend till smooth yet liquid and then all you have to do is squirt this stuff in like it was a differential. I personally trust the original manufacturer instructions …. and for 26 years I have never had a leak …. well, from the steering knuckles anyway!
In the differentials use what is specified by the manufacturer. All of the parts (transmission, transfer case and differentials) take SAE 90 (32F and above), or SAE 80 (32F to 0F) or SAE 70 (below 0F). Here I have compromised and usually go with a "mixed" blend rated as 80w90. You can also find 75w90 but I doubt many would need that. And of course at places like NAPA you can find straight 90. But do stay away from things like 80w140 as this may help your components generate excess heat and lead to failure. I believe this is what I was running (Before I knew better) when my T-84J transmission suffered major tooth failure on the cluster gear.
If the knuckle is a Rzeppa, I know for certain it will not just come apart in your hands – except maybe it is damaged. I do the work generally by myself so I do not have hands three, four or five to pitch in.
Read the manual, read the manual then read the manual … ask questions. Do it! You will be surprised at how easy this is. I have taken apart the entire knuckle and king pin assemblies and installed all new parts and set the tension, etc. It took me awhile but was not all that difficult.