Very easy and pretty safe if you are smart. With your knowledge of computers this is a cake walk.
Basiclly this allows you to load apps that are not apple approved. There are more "app stores" then just apples. Plus there are apps that do things that apple does not approve of such as tethering.
The first step is to go to
www.spiritjb.com and jailbreak your phone. They you load the Cydia app that is a new app "store". There are other app "stores" such as "rockyourphone" which has the mywi tethering app.
here is a cydia walkthrough
http://appadvice.com/appnn/2008/07/how-to-use-cydia-a-walkthrough/You can also now change the look of your iphone with themes which is fun.
One important note is that jailbraking inables SSH client which can open you to worms and such. Because of this you need to change your passwords as all iphones have the same password 'alpine'. You need to change both the login passwd and the root passwd. This is done with the mobile terminal app which is also very cool.
http://www.redmondpie.com/how-to-secure-your-jailbroken-iphone-from-ssh-hack-9140084/anyone else? Spiritjb could not be easier. Also if anything does go wrong. You always can facotry reset and you have the iTunes back up. Make sure you get a jailbroken app back up app. Finally do not upgrade your firmware untill the new jailbreaks have been released.
Have fun. Apple is not the boss of you.
