Does anyone have the definitive guide to jailbreaking and unlocking a 3GS?

I recently gave my carrier locked iPhone 3GS to a friend of mine after upgrading to a 4S, but it's locked to a carrier different than the one she prefers, and is interested in a hacky method to unlock it. I'm not up to date with this stuff, can a knowledgeable soul lend me a hand? It's running 5.0.1 if that helps.