Looking to buy a new vehicle, ext. warranty? rust protection?

[Kracka]

No & no. Waste of money. They'll profit more off that stuff than they will the entire vehicle. Chances are you won't own the new truck through the full factory warranty anyway, and even if you do, you can buy an extended warranty then if you deem it worthwhile. The rust protection is likely a jug of snake oil. Keep it waxed and do a decent carwash with underbody chassis spray every 1-2 weeks in the winter and you'll be fine. Rust/corrosion perforation is covered under warranty, and is typically fairly long coverage.