[Arran]

That Candohm looks like one of the kind that you would have to open from the back, however it looks like they mounted the resistors, and the terminals in a strip of Bakelite or phenolic. It actually doesn't look like it would be too hard to get apart if you needed to, a thin flat blade looks like it should slip under where the front piece folds over the mounting plate, if the front piece is aluminum that would make it even easier. In answer to your second question, yes you could bypass the last section, if it's between the next section and ground, it won't do anything if that final terminal stays open circuit.
Regards
Arran