Where about's in West Texas do you plan to hunt? And what time of year? Unless you have property be prepared to fork out a lot of money even for a do it yourself hunt. I live down here and you better be prepared for some rough country and lots of stuff that either pokes or bites. Every bush has thorns, and every critter has teeth. And do not plan on not seeing snakes even in the winter we have killed more than a few snakes in January after an unusually hot week so they do occasionally come out. Also if you are coming in hot weather (which is year round LOL) be sure to drink tons of water, nothing like getting heat stroke on the side of a mountain. And as mentioned above good optics will be required, and be prepared to shoot 300+ yards and I highly recommend that you bring something with a fair amount of power a good ram is bigger than a lot of people realize. So I would bring .308 and above the 30-06 family would work fine or a 300 win mag if you have one. If I remember right there vitals sit differently than on a deer might check that out but I could be wrong.
If you plan on buying a hunt you should capitalize on the multiple species that are abundant here. You might try to get an outfitter that will let you hunt varmints, javelinas, and maybe even a desert mule deer along with your aoudad.
Have fun if you get to go you will have a blast, I have been wanting to go for awhile now but the funds haven't shown themselves yet haha. I wish you the best of luck with your endeavor.