For starters, congratulation on getting you license. Now for the answers to your questions. Contacting ISS on voice (FM) is difficult since the astronauts are real busy and don't have a lot of time to chat on the radio. Most of the contacts made via ISS are packet. You can send you location coordinates via ISS and show up on a web site with you location (
http://www.ariss.net/). It is very cool. If you are quick, you can have a packet QSO with other station within the foot print of the ISS
The IC-2100 doesn't have a 1200 baud data port, so doing packet will be more difficult, but not impossible. I have had good luck with my Kenwood G707. You will need a computer to run the software required for the contacts via packet.
For software, I highly recommend UISS (
http://users.belgacom.net/hamradio/uiss.htm) for sending the digital data packets, AGW Packet Engine (
http://www.raag.org/sv2agw/ ) for the interface between the computer sound card (or TNC) and the radio, and SatScape (
http://www.satscape.co.uk/) for pass prediction software. All of the above software is free.
For an antenna, a 2 meter � wave vertical will work, but something like the Arrow yagi
(
http://www.arrowantennas.com/146-437.html) works much better with low power transceivers.
I hope this gets you started. Good luck.
73 de W4TME
-Tim