Im pretty sure its a direct replacement for the pressure switch that is removed, the new one has 2 little connections on it, the old one only had 1.
1. It doesn't matter which terminal you connect each wire to.
2. Probably not.
3. Same as #1.
I don't know what the instructions look like, you need to be sure the pressure switch they supplied is in the correct port. Since you didn't ask, I assume that's clear in the instructions.