What turnbuckle issue are you referring to?
As for the diffs. Check them when you get the truck. It they feel snug you should be ok. As they break in they are going to wear a little which is normal. If you start to feel too much play in them then you will need to shim them or they will blow. Ive eaten up two sets already. Asystemerror is 100% right about spinning the truck though. If you go wide open and spin the truck so its going backwards and then get on the gas again you can kiss the diffs goodbye.
And never worry about asking a question that might have been asked before. This MT2 thread has a good group of guys and everyone tries to help each other out. Some guys in the other threads could learn a lot from the people in this one.