Central Arizona Mountain Rescue Association can train in WFA. I don't live out there, just googled. Seems like a mountain rescue place probably has good wilderness first aid
Mechanic skills, well, you could become an ASE certified mechanic but that'll take a while and you would still have to adapt to trail conditions.
I'd imagine being out there on trails with other folks, someone is likely to develop a flat tire or snagged brake line. We used to carry the Chilton's and/or factory service manual but today there is YouTube, although with YouTube you could wade through 10 videos made by people who don't know what they are doing for every video you find that is correct
Carry a couple of 4x4 lumber, maybe 2 to 4 feet in length. Carry some thick plywood to set your jack on in the snow, sand or mud. Know how to change or fix those things most likely to break down or become damaged out there in the field.
Jeep communities often have wrenching parties. I imagine Toyota groups have them, too. You can learn a lot by helping others in a group setting where the work is being done in a safe environment, and you can adapt what you learned for when you are on your back in the dirt instead of having the truck on a lift.
Bring the tools with you you would most commonly need - proper size lug wrench, a breaker bar with the lug nut sized socket also. The right size sockets for battery, oil drain plug, brake caliper bolts, attachment points for brake lines. Shock. Screwdrivers or nut drivers. Couple clamps of various size, primary wire. Flashlight, headlight, gloves. Half inch driver and either 1/4 or a 3/8.
Maybe find a local mechanic. It's hard to find good help right now, and if you show an interest, maybe you could work at least a Saturday helping out and learning a bit, too.
Just my 2cents