RE: Bow tuned, now wont shoot for $*#%
Your new cables will stretch, and then the string and cables will be the same as before you bought new ones. IF they put the right size on. When they stretch, your poundage will drop some as well. It does sound like something is squirrely, I would check the brace height, tiller, and double double check to make sure the cables are seated on the cam and wheel properly. Also, check the limbs for cracks, and your rest. Make sure it hasn't come loose or is broken.
Then, once you are positive everything is ok, head to the shop and do some paper tuning, but only AFTER you have shot the bow 200 times or so to ensure the cables have stretched. Once they stretch, they are done. I don't believe they keep stretching.