Glad you had a good time. Getting the RV stuck in the sand had to be troublesome, but you made it through.
I have yet to visit Marietta, but I have been through a lot of the Pilot Mountains. Yes, some areas require high clearance 4WD. Thus far, I have never needed a tow while in Nevada, but I have helped a few people out of jams over the years.
As far as base areas for exploring that area, I am partial to Tonopah. From my perspective, it is centered well for exploration of ghost mines, ghost camps, and ghost towns. In addition, there are many active mines within a few hours drive. The high point, for me, is the abundance of hot and warm springs, also within a few hours drive. Yes, there are areas of Nevada with more of everything I mentioned, but I like the area around Tonopah.
I hope your continued exploration of rural Nevada brings you great joy.
Time for coffee.