2003 Honda Civic Transmission Problems?
 

I have a 2003 Honda Civic with 80,400 miles on it. I just had to replace the transmission. This weekend I was driving and my check engine light went on, the car wouldn't shift into third gear, it hesitated when I put it in reverse and it smelled like buring oil. Did the mechanics forget to attach something? Will I need to get another transmission, or is something else wrong? Thanks.

ether they used old oil or the gasket that seperates the oil from the extremly hot part is cracked