my situation is different than yours, but hopefully it will be helpful.
i had an A4 leased in NJ, paid the ridiculous upfront tax on the lease and then moved out of state 1/2 way through the lease. i was able to get a pro-rated refund of my prepaid sales tax (~1,300) from the NJ tax department in trenton. it was a PIA requiring several calls and document submissions, and it took about 4 months.
take a look at the faqs: http://www.state.nj.us/treasury/taxa...reamfaqs.shtml
just start calling. it doesn't hurt to try.