1999 5.9 cummins rear main seal replacement

I have removed the rear drive shaft (I was unable to separate the u-joint yoke at the rear axle? I disconnected the bolts and pulled, pried, sprayed penetrator, pried, banged with mallet, pried. There is significant leakage from the rear output shaft, inspection cover, and rear case seal. I ended up busy with work so the truck has sat in the garage. I can take pictures and build a simple walk-through if that would be helpful. I searched for a tutorial on transfer case removal/repair and couldn't find one (sorry if one is floating around out there). What should I look for when I have the transfer case out? Should I rebuild it or replace any commonly worn parts? I wish I had run across the truck before the transmission was replaced, I would have had a built one installed so I could modify the engine without worry of blowing the thing up. I haven't noticed much if any issue with the 4 wheel drive or shifting, other than high reving before shifts in the cold. I'm not impressed with the expense of replacement seals at about $40 a pop for each one!! oh well. I was able to locate a repair manual and have been reviewing it but I was hoping one of you that have done this a time or two could give me some advice before I get myself into a corner. I've done a fair amount of automotive work and I'm confident in my abilities, but I have not done much (independently) on transmissions and powertrain components. Is it normal for the fluid level to be past the full mark all the way to the bend in the metal? It remains this high under running and non-running conditions. I have not been able to find any signs of leakage from the transmission, though I did notice that the transmission fluid level seems high. The truck had a new/rebuilt transmission put in it in November of 2012 and it now has just about 2k miles on it. My transfer case has sprung a leak over the past couple hundred miles. Truck info: 1999 with 90k miles and automatic transmission.

1999 5.9 cummins rear main seal replacement