WOW - great deal!
I can't answer the tx/g3 question, but I had a NexStar and here are a couple of things to look for:

Airworthy - check CG, pull on the control surfaces to make sure the hinges are ok, test surface deflections, range check. Basically do a thorough preflight check.
Landing gear - pull hard on them before every flight. Some had a tendency to come out. It seems the holes in the struts were too small. Drilling them out a little fixed that.
AFS - (1.) just unplug it or (2.) remove it all together and put clear packing tape over the hole.