First things first you need to confirm which firmware your iPhone has - you can't do this from its serial number. Go to Settings --> General --> About. Where it says Version, this is the firmware version number. Mine for example is Virsion 1.1.1 (3A109a)
SSH stands for Secure SHell. Quoted from Wikipedia '(SSH) is a network protocol that allows data to be exchanged over a secure channel between two computers.' Its basically a way to securely remotely connect to another computer (yes your iPhone is a computer) and run commands.
If you have 1.1.1 firmware and you want to unlock your iPhone, go to http://jailbreakme.com in Safari then click Install. Safari should quit and your iPhone should do a soft restart after a couple of seconds. Press the home button and you should notice that you have an installer app on there now. Look for anySIM. I successfully unlocked my iPhone back in September running 1.0.2 firmware, then last Saturday upgraded to 1.1.1 and used Installer to install anySIM and unlock my phone again. (I had to relock the phone to go from 1.0.2 to 1.1.1)
Hope this helps and good luck! Its really not as scary as it appears to be
