Dodge Neon Transmission won't shift

I'm having trouble with my girlfriend's '02 Neon transmission. I'm hoping you guys could help out. I don't know squat about transmissions unfortunately.

Here's what's been going on.
It's been shifting hard at random for the past year. When I mean hard I mean HARD. It's a big kathunk and jolt. Well today it was going into third I believe, then either slipped or went to neutral for a second, and then stuck in second. Which is limp mode I believe?

I have a code scanner at work, I'll bring it home tomorrow and update this post with any codes that may have been thrown. The check engine light was already on due to an evap code, so I can't tell yet if it threw one or not for the trans.

Is this a solenoid problem? Or is the transmission shot? I can't afford to replace the transmission right now. Is there enough evidence towards it being the solenoid to try and replace the solenoid?

Thanks,
Drake