[Aerkuld]

With that lower mileage on a 1999 I would think that the warranty would be a very good idea. If I understand correctly there are several issues that may or may not show on the 3.4 engines. With mileage at less than 10k then they haven't really been given an opportunity to show up or be corrected.
Make sure the service history ties in with the mileage. These cars are very well built and will easily hide higher mileage. My 2002 has 50k on it but several people ask me if it's new - no I'm not joking!
Other than that I have to agree with Mookster on the Pre Purchase Inspection. If the seller is as good and honest as you think then they'll have no problem with you taking it to another shop for a good looking over.
Good luck and don't forget to post the pictures.