1997 Dodge Neon neon wont shift into gear unless revved up

i have a 97 dodge neon with 82,000 original miles on it. one day the transmission just started slipping and dumped all the tranny fluid and some oil. it will go into gear but only if i rev it up and once it catches the revs go down and it slips out. plus my brother accidently put the car in reverse while he was going 40 but it worked for a while after that