Modeling large scale desert terrain

I need to model a large area of desert terrain (similar to the Arizona desert with plateaus and canyons). The only tutorial for blender I found showed how to make a few sand dunes, which is not the scale I’m looking for.

Here are my specific questions:

Should I model all of it or is there a way to procedurally generate some of it that doesn’t need as much detail?

My intention is to have a wide angle shot showing a panorama of the area and then zoom into a specific part of the scene. What’s the most efficient way (modeling-wise and rendering-wise) to do that?

I would give the ANT landscape add-on a try, it can create some pretty nice looking terrains and will save a lot of work.