Stock 79 would be a Dana 20 (I'm assuming you meant you didn't know the model, not what the transfer case is). Any of the major vendors will have rebuild kits for them. It's also a good time to consider some upgrades: TeraLow and/or TwinStiks.
Rebuilds are simple, if you have access to a shop press, even simpler. You will need a dial indicator and magnetic base to set the end play. Other than setting the end play, the most difficult part I found was tightening the nuts on the yokes. Make yourself a spanner wrench:
And have a 'big friend' help. Or a small friend and use an impact.