well currently jailbreaking a 3G or 3GS (3.1.2 fw or lower) is a 1 click job. if you can plug your phone into the pc and turn it on, i think you can handle jailbreaking it.
unlock your phone for free.
you need a wireless network to do this:
-goto
www.blackra1n.com click the windows icon. download blackra1n.exe to your pc
- connect your iphone to pc, (make sure iTunes is off) run blackra1n.exe, hit the "make it rain" button. wait for your phone to reboot.
-turn on your wifi. hit the blackra1n icon on your phone. (black water drop)
-select "cydia" it will install then probably reboot your phone,
-hit the blackra1n icon again on your phone then choose "snow" this will unlock your phone. if you have issues with wifi after just reboot your phone.
you now have a jailbroken and unlocked phone for free.