1) For the most part, yes. But you should take note the CRT Tube numbers and see if they match; they should. The socket should should also fit as well. The problem, if any, is the yoke assembly and the holding tabs.

But you should save your crt with burn because they are no longer being made, and having a CRT with burn is better than having no screen at all.

2) For me, a minimum of 4 days, even though Classic/Classic II has a flyback transformer with a bleeding resistor which would drain it in a few minutes after being turned off. It is best to get/make a CRT Discharge tool and use it when you are not sure if the caps are charged or not. The problem is the Caps, they hold the charge what gets amplified by the flyback transformer.

Worse comes to worst, you can take the suction cup of the tube and bring it to one of the hold down screws if you think it is still charged. If it snaps or pops, it was charged and now has been discharged. Silence means that it was already discharged.

Now, what's wrong with the Mac Plus that is dead? I believe that most machines can be brought back to life. It depends on the resources and time one has to fix them. But... lets get the SE working and then the Classic II and then the Plus.