The Price Negotiation is on you, I hope you score a Good Deal.
As far as the lien goes, if you decide on a price, and ready to buy. Then you both Go to the Bank Branch that holds the lien.
Let say you are buying a car for $10K, he still owes $8k. In this case You can write 2 Checks, one to the bank, and one to Him $8k and $2k Respectively. Then he will have to send you the title once received.
Or
You Write him a Check for $10k, He Deals with Bank, then Sends you the Title when he gets it.
Regardless, you will not be able to get the title Directly from bank.
To Protect yourself, have the bill of sale notarized at his bank.
As far as Transporting, You can go online to DMV website, and purchase a "Trip plate" I think cost is about $8, you buy online, and print it.
It will allow you to drive a vehicle from one location to your home. Good For one Trip (just tape it to the back window)
Then after you get the title, you can register it. (If you were buying from a Dealer in NJ, they could issue you temp tags)
Good luck with your purchase!