Newbie Here!!! Need help DOWNGRADING iPhone

[nevermore727]

I have an iPhone 3G running 4.0.1. It's a lot slower than previous 3.1.2 I had on it. I would like to downgrade to 3.1.2.

Could someone possibly give me a step by step of how to do it?

I have read through similiar posts but everyone asking for help seems to have an inkling of what they're doing and I don't. Also, it is jailbroken (using jailbreakme) if that matters. And I don't necessarily need it jailbroken again - just want it down to 3.1.2.

Thanks

[iYeow]

Put your iPhone in dfu mode
Shift + restore to 3.1.2
Use kick out of recovery from tiny umbrella
Run redsnow 0.9.4 to jailbreak
Now you are back to 3.1.2

Sorry I am on my iphone