New and need help

Okay so I am FINALLY getting in gear to fix my credit. There are a handful of problems I've seen. I pay for Experian FICO and can pull my report whenever. Well I've noticed its reporting 18 accounts (4open - 12closed). There's a bunch of those closed accounts reporting potentially negative when it's PAID OFF. I refinanced a few loans a couple times and they are reporting every time (can't I have them taken off if they were the same account- never closed, never late and open for longer then 18 months before refinanced). Now there's a few that are reporting late payments- I bought a new car and the pay-off check was sent- they are reporting I was 60 days late. There's one I have no idea what it is just says Legally paid in full for less then orginal balance. (I can dispute that right).

I'm prepared to write as many dispute / goodwill letters as needed. I just need to make sure I'm going in the right direction first.

Thanks guys!!