First of all, contact your local DMV to find out what the sales tax rate is, what the title, registration and any other fees related to the purchase would be based on registering it in your home state. Also get the mailing address where they would have to send the check and all supporting documentation.
Give CW this information so they can work the #'s based on the vehicle being registered in NC.
Second, insist they provide you with a signed buyer's order by a manager before you leave home. This will give you the final sales price with all the appropriate TT&L included. It will also show if they're trying to slide any "dealer added" fees into the deal. If they won't do it, walk away.
Third, have them stipulate on the B.O. that the deal is subject to your final approval based on the walk thru of the unit and any and all issues MUST be resolved prior to you signing on the dotted line.
It's not rocket science and the dealer can make it easy or hard depending on their integrity. I was in car sales in a previous lifetime and I had people come from several states away to buy from me. If it was used, then I would send them multiple pics of the car including every dent, scratch or imperfection and I wouldn't hide ANYTHING from them. I would even pick them up at the airport if necessary.
My belief was that if they were willing to invest $$ to buy a car from me sight unseen and sometimes to travel several hundred miles to get there, then I would be go above and beyond to not disappoint. I never had a single customer complain that I didn't tell them everything. I don't know how much of these ethics still exist nowdays.