What trails are on your list? A lot of the trails in Moab are close to town and there are parts stores in town that carry most items you might need, plus several 4x4 shops that can help as well.
When I first started wheeling, I had the same concerns, "what should I bring so I don't get stuck" After wheeling for the past 5 years all over CO, been to Moab several times, etc., I've probably become more complacent. I've been stuck way more times than I've broken down. That's why we buy Toyotas - they don't break
I wheel a 200k mile 4th gen and my son wheels a 300k mile 3rd gen. Keep them maintained and they just keep working - off road or on road.
I still bring a full tool box but don't bother with CVs and all the other parts that might break or go bad. For example, a broken fan belt or ruptured hose isn't going to happen on the trail anymore than on the road and if maintained, won't be an issue on the trail. If you get a flat tire, that's what the spare is for and it's more likely the side wall or tread will be torn and plugs probably can't repair the tear.
If you do break a CV, you probably will need someone to pull you out to a better spot for repair so recovery gear is just as important as spare parts. I've used recovery gear on the trail, never parts. Having the CV would help if the local store doesn't have it or is closed for the day.
With fluids, if you lose fluids, you are either already leaking and carry fluids and if you don't leak, our rigs don't start to lose fluids going off road unless we hit and break something. In that case, you would probably need to get the part you don't have and then you can get the fluid you need to make the repair at the same time.
As someone else mentioned, probably best to avoid doing a bunch of changes just before you leave if you don't have time to make sure they are working as expected and no issues - those items are the ones more likely to cause issues on trail - something comes lose, doesn't work as expected, etc.
You mention concern about grip and center diff lock - what is the concern? I typically wheel Moab in 4 low and keep center diff locked unless I need to take a tight turn/turn around on slick rock. I know some like to engage and disengage CDL but I've found that when I really need it, it doesn't always lock so then I have to go back and forth and mess with it - it's just easier to stay locked and unlock for the rare tight turn or turn around on slick rock.
Moab is an awesome place - Enjoy!
