1989 Toyota Camry I Dont Understand

Im a college student and know little about transmissions. I've just got my transmission rebuilt for $2,290.87. Im only 20 years old and because of my age and lack of knowledge of transmissions I feel as if the repair shop is getting over me. Is that a reasonable price. Now I was told that the differential had alot of heat damage. And it was replace. I'm so fustrated because I dont have much money to give out. It was recently repaired but later that day, at a traffic light I push down the gas pedal and the car proceeded to move then, all of sudden the transmission or the differential locked and I had to send it back to the shop. Why did that happen if I was told it was repaired with brand new parts. Now these are the prices of the parts (Banner Kit $397.55, Torque Converter $275.00, Hard parts $ 248.70). Now what is a Banner kit?. Should it cost that much. In all, Labor $1,250.00, Parts $921.25, Gas, Oil, Grease $65.00, Shop Suppiles $32.00, Misc $50.00, and Tax $72.62.I did the math and that does not even add up to $2,290.87. Also I want to ask the right questions to the mechanic but I dont know what to ask? Can you also help me with that. Also one more question do the Wheel bearings have anything to do with the Differential or Transmission?