Skamper was bought out by Thor Industries in the mid-90's and Thor chose not to continue the brand. That kinda limits any "factory source" for parts. There are, however, websites devoted to the Skamper brand and that might be a good place to look/inquire about parts availability.
Relative to the off-roading, I don't know for sure. My gut feel would be NOT to take it off-road due to its age, construction, and the flexing it will see on uneven terrain.