Jailbreak 3gs, stuck on emergency screen, what next?

[S11DJ]

I've just bought a second hand 3gs.
I'd like to unlock it for my network so i'm trying to jailbreak it.
OK, i just ran f0recast v1.0 to find out this info.
it reads:

baseband 05.15.04
bootloader 6.4
Model MC131

Unlockable NO
Tethered MAYBE

firmware 4.2.1

I've read something about greenpoison, will that work for me??
At the moment the iphone is completely block, just to reiterate.

[jimilee]

5.15.04 is not unlockable yet.

[Mountainmasher]

Greenpois0n will only jailbreak not unlock.

[S11DJ]

So i could at least jailbreak it now and use it as everything but a phone, and then when the unlock is released for 5.15.04, i can then unblock it..?

Should i just follow the online directs for jail-breaking with Greenpois0n or is there anything particular for my setup??

Cheers.