[Arran]

I think that the EPDM covered wire costs more then the vinyl covered stuff, I haven't bothered to search for it since I have several 100 foot rolls of 18 gauge stranded to handle most of the rewiring jobs such as replacing speaker or eye tube cables. The wires on the pushbutton assembly are probably something like 20 gauge solid core wire, if the insulation is melting off that isn't very attractive, but the assembly isn't really carrying any voltage, so as long as nothing is shorting out you can ignore the bare wires, if you want to replace them, or sleeve them, do it one wire at a time so you don't get any of the dozen wires mixed up.
  With regard to the filter condenser can, you can restuff the original, and there are several different methods for getting them apart and removing and replacing the contents, or you can install a terminal strip in it's place under the chassis, or if you are very lucky find alternative places to install the individual caps. The latter will often not work since in sets with a field coil speaker they often have the two field coil wires from the speaker cable routed directly to the terminals under the condenser can, so you are still stuck with either splicing onto the original wires or adding a terminal (tag) strip. One that you easily could leave out of the filter can is the cathode bypass cap used on the power output tubes, if this set has one, that goes straight from the cathodes to ground, in this case the chassis, then you only need to work out what to do with the three filter caps.
 Some guys can cut open a condenser can and restuff it without even removing it from the chassis, I guess if you have a pipe cutter that will fit around it you can do this, or you could wrap tape around the can to act as a straight edge and use a Dremmel tool cutting wheel, or a jeweler's saw. Then they either couple the two sections back together by inserting something inside, like thin wall tubing, or by using HVAC aluminium duct tape on the outside. Other people remove the twist lock can and uncrimp the bottom, I tried this once on a scrap can I had laying around and it is not easy, plus at some point the capacitors inside will have to be replaced and the can will have to be reopened. If there was only one cap inside this would not be a problem as you could use a large film cap and never worry about it again, but not on a four section can. I think that cutting the can open neatly, and then coupling it back together is probably the best method, then it's not to hard to get it open again, and if the line is neatly cut nobody will see it anyhow. I did this once with one of those older types with a threaded base that someone had hacked apart, I had to take both halves of the can, and cleaned up the jagged cut with a file, and then coupled the two halves back together with a PVC coupling slid into the inside, then secured the two halves of the can back together using the coupling and some hot glue. I didn't have to use a PVC coupling, but it just happened to be the exact size as the inner diameter of the condenser can I was repairing.
Regards
Arran