[Arran]

 If the resistors are in good condition and measure within 10% (some go up to 20%) I would leave them as is even if they are of the dogbone style. Believe it or not some dogbone BED coded resistors were quite stable, most were not, but in any even if they haven't drifted in value after all this time they likely never will.
 Regarding the leads into the IF cans, by all means replace those, the primaries often carry near or full B+ voltage so the wires shorting to the chassis will not be a happy experience. One part that you may want to take a closer look at is that square molded capacitor connected to one of those rotted IF can leads, it says "Micamold" on it, it may be a mica cap or it may be a small paper cap, check the parts list to see what value it is.
  As for the electrolytics, don't even bother trying to figure out the state of mind of whomever put those in there, just take them out, test them, and if good hook them up the way the factory intended, or order some new name brand radial lead jobs to restuff the original cans. The way they have them mounted is just moronic, the connections are made in mid air to some original wiring, that's a big no no given the voltages they handle. It would not surprise me if the reason that the set hummed was due to a wiring error, particularly on the negative side of those filter caps, sometimes the chassis is not the most negative point in the set.
Regards
Arran