Need Tran. Help!!!

I was driving my duster the other day 408 SB 904. And it feels like the trans went out. I have never had a transmission go out before so I don't know how it feels. when the car is hot it won't go in gear, but if I shut if off for literally 1 minute, it'll drive for a little and then start to slip. Does this sound like the transmission is bad, or do you think it might just need to have the bands adjusted? I need all suggestions please!!! THANKS.