I am ready to install new electrolytics on a 1960 Magnavox,
and just bought 20 gauge solid wire, which when I spliced it, is copper.
But looking at it, I don't see one piece of copper wire on the chassis.
Is the old wire copper coated in nickel?
Does it need to be? Just want to be sure before I go ahead and solder everything. Thanks!

All the wiring in the set was refered to as "tinned copper wire". It was easier to solder.

You can, but beware that the copper conductors will eventually corrode. Some of the wire in my CTC-5 was like that, it causes breaks.