Hi jc6905,
Welcome … and I’m glad you found us 
The first place I would start your research is the mattress shopping tutorial here which includes all the basic information, steps, and guidelines that you will need to make the best possible choice … and more importantly know how and why to avoid the worst ones.
Two of the most important links in the tutorial that I would especially make sure you’ve read are post #2 here which has more about the different ways to choose a suitable mattress (either locally or online) that is the best “match” for you in terms of PPP that can help you assess and minimize the risks of making a choice that doesn’t turn out as well as you hoped for and post #13 here which has more about the most important parts of the “value” of a mattress purchase which can help you make more meaningful quality/value comparisons between mattresses in terms of suitability, durability, and value.
Once you get to step 3 in the tutorial if you let me know your city or zip code I’d also be happy to let you know about any of the better options or possibilities I’m aware of in your area.
Phoenix