Jailbreaking Help (most info sites not specific)

[Kanegasi]

I was first introduced to jailbreaking when I used SpiritJB on my 3.1.3. I've been sitting on my iPhone for ages now and I would like to upgrade to iOS4. Honestly, the only reason why I want to keep jailbreaking is the fact that I can't customize the default SMS tones which really annoys me.

Now, like my profile says, I'm using Windows 7 Pro, and my iPhone is a 3GS with 3.1.3 and a modem version 05.12.01. I am not interested in a carrier unlock since I'm comfortable with AT&T... for now, but the thing I want to accomplish is a deeper jailbreak than SpiritJB. One of the custom things I wanted to do when I jailbroke the first time was to change the startup screen and the charging screen, but I found out SpiritJB just allowed me to run Cydia and not do anything to the bootrom.

In short, my goal is to jailbreak from the bootrom rather than just run Cydia. How do I go about this? Can I do a clean install from iTunes to the most recent iOS4 then downgrade with the blobs Cydia has saved for me?

Thank you in advance for your help and especially patience if this post isn't new.

[iYeow]

Yes, you should download tiny umbrella and click save shsh first. Then you have to check your bootrom type, whether new or old bootrom. You can check it from here
If you have the old bootrom then you can install boot images using redsn0w or choose custom images while building your CFW.
With all your available shsh blob and if you do not need an unlock, you can choose whether to restore to 4.1 or 4.2.1(tethered jailbreak if new bootrom).
You can use redsn0w 0.9.6b6 to jailbreak and install boot images all in one after the restore thru itunes.

[Kanegasi]

So as long as my bootrom is iBoot-359.3 (from the link you posted) I shouldn't have to worry about the jailbreak being tethered and I can fully upgrade and restore from iTunes, then downgrade using the blobs, then jailbreak as mentioned?

EDIT: just found out I have 359.3.2, so if I want an untethered jailbreak, I'm stuck with 4.1 for now, correct?

[iYeow]

Yes, you will get a tethered jailbreak at 4.2.1 and your iphone cannot accept boot images because you have the newbootrom.

[Kanegasi]

Bringing this topic back up, I have the same details:

3GS
3.1.3
iBoot 359.3.2
modem 05.12.01

I'm still not interested in an unlock and would still like a bootrom jailbreak rather than a userland one like SpiritJB was. greenpois0n can apparently do that.

Now I have tinyumbrella and greenpois0n and my host file has "74.208.10.249 gs.apple.com" in it. From here, I just do a clean restore to 4.2.1 (Cydia has my SHSHs), let greenpois0n do it's magic, and I'm fine? Will I get the ability to do custom boot logos? Is there anything I need to know specifically, or does my situation fit the various jailbreak steps found on this site and others like iClarified?

Thank you for your help.

EDIT: nevermind, everything went smoothly... 4.2.1, greenpois0n, Cydia... perfect