Hi Lori,
Some of the better options I’m aware of in the Minneapolis area are listed in post #2 here.
I don’t know specifically how knowledgeable each may be outside of the comments there but the information on the site and that is linked in post #1 here can act as a “fact check” to make sure that what they tell you is fact based and not just based in their desire to convince you to buy a mattress from them.
The most important part of buying a mattress outside of making sure that you test it carefully and objectively for PPP (Pressure relief, Posture and alignment, and Personal preferences) is to make sure that you are able to find out the quality specs of every layer in a mattress you are considering because that way you aren’t dependent on “opinions” or “marketing stories” and you can tell the quality and value of the mattress and make meaningful comparisons for yourself regardless of the level of knowledge of the retailer. I would certainly be more inclined to deal with a retailer that had the experience and knowledge to help me make good choices though and one of the most reliable signs of better retailers is one who understands the importance of knowing what is in your mattress, is comfortable talking about it, and makes it easy to find out.
Phoenix