2003 Dodge Neon Neon speedo/tranny issue

The problem started about a month ago. While driving the speedo would go crazy and within a minute or so the tranny would go into low gear. I would have to pull over wait a few minutes then start it up and it would be ok. It would do this several times in one day or go days/week with no problem. Today I tried to start it and the battery acted dead. I jumped it and it started but sounded aweful, like it wanted to die. When I shifted to reverse it moved a few feet and nothing, then I ;put it in drive and same thing. Now it won't go in gear at all and when I turn the key on without even putting it in gear the speedo goes crazy. Please please help. I don't know where to even start. I'm a single woman living alone and this is my only transportation, also I don't want to get ripped off by a garage selling me fixes I don't need just because I don't know anything.(It's happened before). Thank you in advance for any help