You must bring all appropraite items as well as ID to a local branch.
If it is within 60 days of lapsing, you can just come to a branch.
It has been more than 60 days.
Unfortunately, no relevant information is found.
You have to go to the branch where you originally got them, then, with the necessary information and credentials.
Though it sounds like you have a basic idea of the necessary requirements, so just make sure you go back to where you got them from in the first place.
Do I have to get rid of liability?
I can not recommend or give advice about coverage, I can only direct you to the relevant authorities.
Is the any sort of credit towards the payment of the New York State sales tax if I bought my ATV out of state and paid the state sales tax for that state?
Yes. You can apply for a credit when you apply for registration in New York. However, you can only be eligible for this credit if New York and the state where you paid sales tax have a reciprocal sales tax agreement.
III didn't buy from a dealer. I bought from a private individual. What would be considered an acceptable proof of ownership in my case?