did you pay new york state sales tax to the leasing company?
Yes
in that case please provide your lease stating that you paid New York State sales tax and complete the Sales Tax Exemption Claim {Sales Tax Form} PDF [5] at the Department of New York State Tax and Finance DTF-803.
and where do I have to make that request?
Take your completed registration application and additional documents to a local DMV office
Do you know about NY State vehicle registration, and what can I use as proof of ownership for a trailer model 1976?
for that case, you can use either the NY State Certificate of Title (original or a certified copy) or a acceptable proof of ownership from any other state.
Ok, now I need to know about the proof of ownership for snowmobiles purchased from a dealer.
for snowmobiles purchased from a dealer, you can use as proof of ownership the Manufacturer's Certificate of Origin or the Manufacturer's Statement of Origin. There are some more options.
What in case the owner dies. How does the transfer go?