Welcome to Newmar ownership.
WOW...you have a lot on your plate and I wish you the best outcomes in all that you can control and the ability to handle that which you can't.
Perhaps this is a very basic starting point but go to Parts & Support - Newmar
and near the bottom left of that page click on the box for "Access ComNet" That will get you into an area where you can search for parts (Specific to coach SN or drill down by year and model) and some technical information.
By "4 season" they are saying that it CAN endure a lot of the seasonal weather. Newmar has some of the best coach insulation found in the production model industry. Even with that being said, extremely cold weather might require you to winterize your water system. Even if you have tank heating pads your water bay pipes are at risk of freezing during very cold weather. If you have a blower switch to divert some of hour furnace heating into the water bay you can probably do well down into the lower 20s as long as you run the furnace. Some folks run a power cord into the wet bay to either power a light bulb or space heater. This works well for many while on shore power but you will probably need to run your generator to provide AC to a coach outlet to run something like that while driving if it really THAT cold. If it is THAT cold...you will probably be parked somewhere. LOL
Being in central OK and traveling to the TX panhandle you will be seriously challenged by cold weather. You may want to consider blowing out your system instead of antifreeze if you think you will be in and out of the coach. There will be a few more challenges such as making sure "out of site" pipes (like the line to an ice maker or under sink hear walls) are also blown out and/or can be isolated and turned off after being blown out. BTW...if you have heat pumps they will need shore or generator power.
ALSO...you will need shore power for your block heater! Depending on temps and your preferences, you may need to run that as much at 12 hours before a really cold engine start. There are LOTS of opinions on their use but I use mine if temps have been at or below freezing for more than 8 hours. I will run it for at least 4 hours before a planned engine start and add 1 hour for each 2* below freezing up to 12 hours.
You will go through a fair amount of propane. If you have heat pumps they are only good down to about 35*-40*. I normally switch from heat pumps to the furnace at temps below 40* because they get progressively less efficient as the temps drop. While you are driving you will have full use of your furnace along with dash heating. There are lots of tips on how to be as comfortable as possible and protecting your coach systems throughout IRV2. Use the SEARCH feature liberally.
Work your way through you're essential systems and I would consider the generator as being right up there with chassis and basic home features. You do NOT need the generator to run the furnace while driving. If temps are above 40* and you have heat pumps you may find that more economical and reduces the number of propane fill ups you will need through the cold time. Again, if you run some kind of light/heater in the wet bay while driving, you will need the generator running unless you have a those on an inverter circuit and your space heater is relatively small in power needs.
I'm certain there will be lots of other tips heading your way.