Ok so it has been a long while since I posted...and I'm bringing a thread back up from the dead just for an update. Sorry it took so long, but the yukon seems to be a-ok as far as starting, and charging goes. I think it was the starter. It eventually broke one of the starter bolts, and one of the starter wires was actually loose I think. I'm not sure, but it's good, has been for a little bit.
I do have some new questions though.
Our heater only works on the 4th setting, and it comes on whenever it wants, at random and we have no idea of telling when it'll come on until we feel it blowing at us. I think someone told me before once that it's some kinda resistor in behind the glove box somewhere? I was wondering if anyone had a picture of the actual part/piece/wiring...etc. Mainly because I plan on going to the junkyard tomorrow, and was hoping to just take one off another yukon/suburban...haha