2002 Dodge Neon won't shift

I have a 2002 Dodge Neon that I bought brand new. I haven't had too
many problems with it (it has 80,000 miles) but it has always seemed to
have a jumpy feeling (for about 2 years) when it shifted. I had it
looked at numerous times and they couldn't find anything wrong. A
couple of weeks ago, it had a crank shaft sensor that had cracked and I
replaced it. Now, only yesterday, it started getting really jumpy on
the ride home. Now when you start the car and try to shift, it won't
even go into gear. The engine revs and it still starts just fine---but
it will not go into gear to move. My dad thinks the transmission is to
blame, but I hate to think that at 80,000 miles it needs a rebuilt
tranny. It had the solenoid pack replaced while it was under warranty
at about 50,000 miles so would that have influenced this problem? I
was hoping that someone could share some idea as to what might be wrong
here as I get lost with the transmission system. I would appreciate
any feedback.