Here is a scan of the custom's invoice for my 87 that I imported in 2004.
Pointman
Yes, they still charge a duty & call it a duty. See Box 33 & 38 above. 6.1% for cars from Germany. You also pay $100 Excise tax for Air Conditioner.
It has to have a clear title (no liens) to clear US Customs. If the PO has a loan against it, that is registered against the title. The loan would have to be paid in full & title cleared before importation. I don't know the procedure so check with the state's DOT & US Customs before proceeding.
And yes, if the VIN plate confirms that the car was actually made more than 15 years ago RIV is not necessary. For example, as of today, May 21, 1991 would be acceptable.
Strugs
Bank to bank transfer is all that works for fast & safe cross-border payment. I got all banking info from the PO & I verified execution with her bank manager a couple for hours after the transfer. It was easy but there is an element of risk because for a brief period, you won't have the cash or the car.
Ian