Pontiac Grand am Fluid Leak Lost Gears

Hi , My car was leaking transmission fluid from cooler line I lost reverse and then all forward gears. I did have replace however the check eng. Light, serv. Vehicle soon ligh, abs light and trac off light are all on car will not shift into any gear and will not move at all rpms just rev high
I have been told transmission is bad and needs to be rebuilt however no one is checking my lights on for codes
Is it possiable transm could still be ok and that problem good be something else
Trying to find out wether car is worth keeping or junking
Thank you hope you may be able to help