Ken grutza

I have a 1999 Chevy Tahoe with about 270,000 miles on it. I have the 5.7 vortex engine with l460e transmission. move noticed my transfer case is leaking fluid. I don’t often use it in 4wd but the fluid is coating everything behind it. I it’s my tow/haul vehicle so it sees about 12-15k miles max a year. (Not a daily driver) move just put a lot into brakes/suspension/axle seals etc and am wondering if a used or rebuilt unit is the better option? I guess first I would need to know Which case I’m looking for? thanks in advance.