transfer case control module (tccm) info please!

Howdy folks, I have a 1997 Sierra Z71 w/5.7l. I've lost my 4WD and I believe it is the tccm. A local shop has traced it down to a couple of parts with the tccm being one. Would there be an after market tccm available? The dealer in the city quoted me $500+ for a new one (I'm a little nervous dealing with them). I tried to search through gm parts direct without success but I generally have a tough time on that site. another question is how would one check out a tccm. Is there a special gm tool to check it out. I've already pulled it out and I am tempted to pry it open to check the insides. Any suggestions.