[old_tv_nut]

(6) - Yes, suitable types. The only caution would be if the voltage ratings were lower than the original (they are most likely OK).

(5) yes, just connect both wires to the plus side of the new one.

(4) The conductive coating ("dag") on the outside of the tube MUST be grounded. This way the tube itself acts as a capacitor to filter the high voltage supply. If it's not grounded, the dag can charge up and arc to other things. It looks like someone fixed a loose or broken ground this way.

(3) and (2): Someone else more familiar should answer

(1) both time and temperature affect the degradation of electrolytic capacitors. So, the NOS might be better but still not good. Safest thing is to replace with new, especially if you have no way of testing them. It takes an old-fashioned tester that applies sufficient voltage to see if they are leaky. A modern low-voltage capacitance meter will not detect this.

PS: after a year disconnected, your only risk of shock is static from scuffing your shoes on the carpet. However, once you do fire it up, it's good to discharge both the lytics and the high voltage after you shut it off and before you go poking around.

Of course, don't do any work while it's plugged in. It's a good idea to UNPLUG the set (not just turn off a power strip) in case it is a hot chassis set (no power transformer) or is a transformer set that happens to have a short somewhere.