How could I SSH into a certain screen, so if I had a server running on a command line I could ssh into that screen from somewhere else to monitor it? Also how do I find out the number screen I'm currently on?

When you say screen do you mean the program screen, right? Cause otherwise what you want to do (monitor an ssh session is not possible (at least to my knowledge)). With screen you do the following:
You run screen then hack happily away and without detaching the screen session you ssh into the box, run screen -x and voila: You now have a shell which accepts input from two different computers. Beware though that both users have full access to that shell unless one detaches from the screen session (CTRL-a d). So if either one log out while still attached the session is ended for both users.

If the above makes no sense to you you probably don't know screen. Follow the above link and read about it there. It's a great little tool.

We were using Sco-Unix in work a few years back and used to use a program called Double Vision, which allows you to connect to a session. So all you have to do is connect to the relavant terminal.
I dont know where we got it from, but we used it to train people to use applications remotely.