Car will shift into reverse but won't move.

My 1997 Nissan quest will drive forward and it shifts out no problem but it won't go in reverse. I was told if the transmission pan gasket got messed up it could cause it to not go in reverse so I bought a new gasket and put it on and I still have the same problem. I was also told from the old lady I got the van from that the reverse was working fine until she hit something and dented the transmission pan and that's when it wouldn't go into reverse again. I seen online that a dented transmission pan can stop it from going in reverse so I'm going to buy a new pan and hopefully that problem is fixed. I will post on her a update when I get a new pan for it.