what are my options?

just bought a used van. has a 30 day warranty. the next day noticed an oil leak. i got an estimate from my mechanic for $460.00 to repair. the dealer refuses to fix it but is willing to refund my money for the vehicle if i don't like it. the problem is i do like it and want to keep it but don't feel i should pay for the repair. also, he's holding up my registration until i'm "satisfied" with the van. if he doesn't fix the problem and i have to, am i justified in suing? also, how can i get him to not hold my registration hostage? i've told him twice i want to keep the van but he still hasn't sent in my registration. what if he keeps stalling until my 30 days are up?

**** U.S. LAW ONLY - PLEASE INCLUDE YOUR STATE BECAUSE LAWS VARY FROM STATE TO STATE.****

new york

new york state

also,

i forgot to mention that it's a 1995 vehicle with 111,000 miles.

What EXACTLY does the warranty say??? I doubt that it is unlimited to the extent that it even covers an oil leak.