As Tim mentioned in the first reply, you have some questions to answer for yourself before you can move along. If your budget can manage it and your main goal is to visit the west, I would fly out and back and concentrate your time in the west. You could easily do a loop trip as mentioned and start and finish in the same City [Vegas, Denver, San Fran etc] or start in Denver and finish in San Fran for example, drop the car and fly home. [You will most likely face a one way drop off fee.]

We can help you route it, once you have figured out what you want to do and places you really want to visit. I'm not sure I would base a trip around the Four Corners Monument though. It's great for a photo opportunity when passing through, but at the end of the day it is just a plinth in the middle of nowhere ! Compare that to the likes of the Grand canyon, Yosemite, Sequoia, Zion and Bryce canyon NPs', Monument Valley etc and it doesn't come close imo.

Once you have a few dots on that map and have decided whether to fly or drive [or a combination of both] let us know and we can help put it together.

Enjoy the planning, it's a great part of the journey as a whole!