The headphone jack is surrounded by rubber. It's kind of squeezed in there. You can pry on it to get it out.

Are you guys kidding me? You are going to get in so much trouble.

Don't get me wrong--this is a super cool thing you've done, but if this guide is still up 48 hours from now, I'll be flabbergasted. So I hope lots of people are mirroring this!

This right here is the $100,000 question. Stick one of your existing AT&T iPhone 4 front assemblies on this bad boy and see if it fires up!

Note where the little rubber thing is. It's there to protect the digitizer and LCD ribbons curving over the top of the mobo. If you do these a lot, you're going to have a WTF moment when you go to put it back together and you have this short rubber strip....

I actually just figured it out. I had the ribbon cable for the digitizer running under the LCD and that wasn't allowing the LCD to sit down far enough. By re-folding the digitizer cable so it was triple-folded (when you do it you'll see what I mean) and only under the glass where there is no LCD, you'll get the glass to sit right.

There should be (in general) better notes about the reassembly process. Getting the thing glued back in is WAY harder than just "reverse this step." Getting it to sit flush with any kind of adhesion is pretty difficult. No real advice other than make sure the edges of the metal thing at the top of the back of the digitizer are in the right slots and use judiciously placed pieces of 3M 300LSE adhesive.

Cracked your front panel? Isn't that what was wrong with it in the first place?

You can leave the sensor stuck to the LCD if you're reusing the LCD. It just stays attached to the LCD no problem.

By it's BOTTOM edge.

Be careful to make sure you don't pinch the clear plastic tab under the mobo when reinstalling. :P