help for printers,public IP?

I have been suffering these two problems in my network.

Q1: i have 25 tables with 2 pcs on each table.I want that if a user
login to a pc on table 19 then the printer on table 19 should be
his default printer.Plz solve this problem. I am using windows 2000 domain based network in the class room lab.

Q2: As I m working in a LAN.and I m behind a firewall as we use
proxy server.I wanna know my gatways machine’s external interface’s public ip address with which i can communicate with other computers on the internet.

I m waiting the solution of these problems
Pls Help me