1) I think if you:

it will no longer start up automatically.

To make it start up automatically at the next boot, do:

You need to issue these commands as root from the x-terminal application, or logged in as root over ssh.

To stop and start the ssh server, use xterm, become root and:

2) No, you can go to xterm, become root, and do it from there.

The settings are in the file
/etc/ssh/sshd_config

you will need to stop and start the server for any change to take effect. Your root password is not part of the ssh server settings and can be changed by running the command passwd as root inside x-terminal.

other 2) No, it will stay as you set it.