Hi Amdavis,
I completely understand how the large amounts of information on a forum like this can be overwhelming and the first place I would start is post #1 here which has the basic information, steps, and guidelines that you will probably find the most helpful.
I’m not sure which mattress you are looking at but “value” is relative to the types of materials in the mattress and to each person’s personal value equation. I think that “average” prices wouldn’t be nearly as important as a specific price of a particular mattress and how it compared to other mattresses that have a similar design and use similar materials that are either available to you in the area or online (for those who are comfortable with an online purchase). Some of the better options and possibilities I’m aware of in the Washington / Northern Virginia area are listed in post #2 here.
I can only speak to the quality or relative value of a mattress because there are too many variables and unknowns for anyone to know with any certainty what combination of materials will be most suitable for you based on “theory at a distance”. There is more about the most effective ways to make mattress choices in post #2 here.
The most suitable choice for a foundation depends on the type of mattress you choose. There is more information about foundations in the foundation thread here and the two posts that are linked in the second paragraph of the first post.
Choosing the mattress I have would be among the worst possible ways to choose a mattress and it isn’t available any more anyway (they no longer supply talalay latex) but if you are interested out of curiosity you can see some of the details in post #4 here.
If your mattress is only two years old you may have some options that can improve it. What brand and model did you buy? I’m not sure what you mean by having a “huge gap” between your hips and the bed?
What are the “symptoms” you are experiencing on your current mattress?
Phoenix