Most of the editors here won't hesitate to crack open their electronics, and that can probably be said for a lot of our readers, too. However, if you're timid about loosening the screws on your iPhone to do a repair (and understandably so), a ScrewMat might give you the confidence you need.
Available for the iPhone 3G/3GS and both CDMA and GSM versions of the iPhone 4, the plastic mat is magnetic so you can keep all your screws and other small iPhone parts organized for easy reassembly.
Perhaps more importantly, though, the top of the mat features an illustrated guide for finding all the impossibly small screws that hold things together. It tells you the stuff not to touch, too.
The mats will set you back $19.99 each through iFixit.com, so you can pick up a mat and your replacement parts in one order. Or you can pick up all three from the manufacturer for $49.99 and start your own repair service.