A few basic questions so I don't start a fire

[Dubis7]

Hi all. Just wanted to get a few basic piece of information written down so I have them available going forward. I've somehow been in this hobby for something like five years and realized today that I've never actually bothered to memorize this stuff.

- What wire gauge is generally used in vintage radios/tvs/electronics? I know there's probably some variation for signal vs. power supply, but are there some numbers that I can usually rely on for different applications?

- When I'm replacing a selenium rectifier with a diode, how do I polarize it? Generally, the rectifier is marked with a + on one side. Does the line for the diode go on this side, or opposite? I managed to burn out an entire power transformer in the past doing this wrong, learned it, and have now forgotten it again so I'd prefer not to repeat that mistake.

- What temperature to y'all generally use for your soldering irons? Do you change it for soldering and desoldering?

- How do I safely discharge a CRT? Is this different for sets with/without a power transformer? I've never had to do that but I've got a set lined up that needs the electrolytics replaced, and I'd prefer to get the high voltage discharged before I take the chassis out.

- When replacing a power cord, the hot side goes to the fuse or switch, right?

I'm sure I'm going to think of more later, but that's all I've got now. Any help is appreciated.