hot water heater died

[xoxoxoBruce]

there are only two pipes: incoming cold water and outgoing hot water. how frickin' hard can it be?

It's not. If the replacement heater is identical it's even easier. But they seldom are, so it might take a couple fittings.

Yes, dry, clean, flux, and if the copper starts to discolor, it's too hot.
When you finish, don't touch it... unlike electronic soldering it takes time to cool. Solder goes through a plastic state between liquid and solid. If you move it during that transition you can ruin the joint and burn the hell out of your hand. It only takes a minute or so to be safe to move, but it's easy to forget how hot it is, because there's no visual clue.

Shop vac the rugs, turn up (down) the A/C, and fans, for the carpeting. A dehumidifier would help, too.