New to jailbreaking and unlocking

[marlon71usa]

I'm new to the jailbreaking community and wish to pointed in the right direction.

I've just obtained an Iphone 4 with firmware 4.0.2 and baseband 01.59.00.

I want to jailbreak and unlock to use with T-Mobile. I want to go to ios5 while preserving my baseband. I see a bunch of programs ending in snow or rain. I don't want to make a mistake and upgrade my baseband. Will the jailbreak and unlock be unteathered?

Any help appreciated...