I want to sell my car to a private party.  
There is a lien on the car.  
The price on the car exceeds the lien.
The finance company will not release the title until the lien is paid off.
I am unable to to pay off the lien beforehand.
I have got an offer from a private party that is good and I am willing to accept.
Now comes the legal/title/registration stuff....
He lives in VT and I live in MA.
Any pointers on how to process this sale legally and safely?

You might talk to the holder of the lien, bank or whoever.  Perhaps
they would agree to receiving the total payment, thus having
settlement of your loan, releasing the lien and giving you the
balance.  The buyer probably would trust this arrangement.  Perhaps
the lienholder could/should take possession of the car to ensure that
it's around for the buyer to pick up.