Well, as for the crock-pot from WalMart, probably the model SCRP500-B since that is the only one I could find for $15, is sold at other stores and online, too. The big problem seems to be that everyone is sold out! It's not going to be as durable or have all of the features of the more expensive models - but it should certainly do what you want to do.
I'm guessing your thinking along the lines of Alton Brown's Overnight Oatmeal
? Yep, pretty good. I'm not a big cranberry fan so I used dried apricots ... yummy. Dried apple and banana chips turned out pretty good, too.
This is something that I would not try to do on a stove in a stock pot! It would probably work in a pot in the oven overnight ... but the crock-pot will not heat your kitchen up and is more energy efficient.