Welcome to the forum and thank you for your service to our country.
The best advice I can give you is, don't be in a hurry and take your time buying a RV. Read and ask lots of questions on this and other forums.
Even buying used, go to RV shows and dealer lots. Look at everything and get an idea of which floor plans work best for you.
Condition is the important factor in a used RV.
Do not take a salesperson's word that something is in good condition and everything works. Their job is to sell you something.
Don't hesitate to ask questions, someone here will have the answer.
Use your search as a learning experience. If you can work the systems on a submarine you can quickly figure out how a motorhome works. :)