I PHONE PROBLEMS JAILBREAK TUTORIALS

I just bought an iphone unlocked off the classified ads, and I want to jailbreak it so I can run cool applications like the nes roms and the video wallpaper. I was under the impression that if the phone is jailbreaked you can see it in my computer, however I cannot so I assume its not already jailbreaked? The guy I bought it from said never update or it wont work anymore, is this true? My version is 1.1.3 and its unlocked for rogers in canada. Is it safe to jailbreak it and if I do will I have to unlock it again or something? And if I screw it all up can I go back to my old settings where the phone actually still worked?

If its unlocked its already jailbroken...most likely...use the new winpwn http://www.winpwn.com/index.php/Main_Page if your on windows or the new pwnage http://wikee.iphwn.org/news:pwnage1dot1_announcement if your on apple and you will b okay