Jailbreaking to design custom UI skin

I'm a graphic designer but have never jailbroken my iphones.

I have an iphone 4 and it's out of warranty so I was thinking of jailbreaking it to design my own custom iOS skin (as I've seen others).

I've never done this but am determined to give it a try. Does anyone have advice on how to do this? The designing part is no problem, I'm just wondering what programming skills (if any) I'll need etc.

Any help is appreciated!

Anyone??

Has anyone designed a custom skin for their iphone?

I think searching on YouTube should give you some idea how the theming works. I haven't done it myself but the general process is:
Jailbreak
Use a FTP program and install your theme.

This is how you Jailbreak it.
How To Jailbreak iPhone 4, iPhone 3GS Using Redsn0w For iOS 4.3.5 [Windows / Mac] – iPhone Hacks

I'll check this out, thanks!

Anyone else design skins for their jailbroken iphone?

Anyone?

Start here
iPhone Theming on WinterBoard - Jay Freeman (saurik)

Or search google for winterboard
Let me google that for you

With iOS 5 out - things are more than likely changing again. There is only a tethered jailbreak currently so I haven't moved up yet.