Mac, welcome to the forums. When you get a minute, drop by the into section and say howdy.
The Mossberg 351 C has a barrel band, loads thru butt. The 351K has no bbl band, loads thru butt. Made from ABOUT 1953-1971. Value for ANY gun is based on exact make, model, and condition. The store brand rifles have a smaller collector following than the name brand- value is mainly as a shooter. Typically $125-$200.
For any parts Mossberg, havlinsales.com is the place. Vic Havlin used to work for Mossberg, he and his wife Cheryl run the Mossberg Collector's Assoc, and are very nice folks to deal with.
For info on just about any Mossberg 22, try HERE: Mossberg 22 LR Models and Specifications