newbie 4x4 questions

[phantom 309]

i have a 1994 k2500 with a 6.5 diesel,.i,ve had this truck for a year,.and i put new universals in the front shaft when i first got it, but thats it,.
I think the trans is on it,s way out,. getting pretty slidey between2-3, i read once that i could add a resostor somewhere to raise pump pressure but i can't find that link now,.
i can get another low mile rebuilt 4l80e but its for a 2wd,. how much is involved to modify it for a 4x4?
what transfer case would this truck have? it seems to hold on to 4 wheel drive even after i shift it back to two wheel,. i have to stop and back up 20-30 ft before it lests go,. if i get stuck i can shift into 4x4,. but often it won't engage till the truck has gone ahead 20-30 ft,. this is pretty frustrating to get pulled a little then all is good,. how do i fix this?
This is really my first 4x4 that i,ve owned, and i guess it,s time to learn how to pull it all apart and fix it,.

Nick
i did manage to do both front hubs and rotors just recently,.