We have flown into Vegas a number of times in the past few years. I am impressed by how the airport is oriented to moving a lot of people relatively fast. The centralized car rental building works well. There are free shuttles to and from. The drive from LAX to Lone Pine would be difficult. The LA freeways will have bumper to bumper traffic.
You do not have to pay to drive through Death Valley. The paved roads belong to the state of California not the NPS. If you stop to view the sights, then you should pay. If you have an annual park pass, you will have to show it at the visitor's center to get a receipt to display in your window. The machines about the park don't take annual passes, only credit cards.
