Armstrong

Have a buddy that has a 350 tranny in an old monte Carlo. He just got it and it goes in reverse fine but not forward. All fluids are good but it just won't ingage. It has been sitting for about three years so I expect the seals are probably shot. Was just wondering if there was a way to maybe soften up or if there was something I'm not aware of that could be the problem. I'm not very keen on transmissions.We were gonna drop the pan and change the fluids or is that just a waste of time?