I've changed out the screens on an iTouch 3, and an iPhone 3GS.
The digitizer and LCD are separate parts, and are relatively easy to replace.
Well, they
are the second time. First time, it's a little worrysome.
I researched the #@*^ out of the subject on youtube first, and had some confidence going into it.
The
best way is to not rebuild your screen assembly with a new digitizer panel for $5-12, but to buy the whole subassembly for around $15-18, and just remount your good & working LCD onto it.
I've done two or three screens on the iPhone 4.
The
only way to get 'em is to buy the digitizer WITH LCD attached.
They go for $28-35 on Amazon.
Back then, the 4S screen wasn't available, but now I see it's in the same price range.
You'd better have warmed up by doing a few iPhone 3 or iTouch screens before tackling an iPhone 4
They are a nightmare!.
I have a setup consisting of a yellow towel, several magnetic sheets*, plus numerous screwdrivers, tweezers, and plastic pry bars.
There are many repair videos and you'd better watch 'em all, because some of them leave out critical steps!
If you drop just one of the two dozen screws,
you are screwed.
I have spare screw kits on hand!
Also, some of the shields need to be cleaned of finger oils before being reinstalled .
Failure to do so, can result in reduced signal strength.
That's not B/S - it happened to me on one phone!
After putting a slightly yellowish screen on my first iPhone 4, I did a comparison with my iPhone 3GS (which still had factory LCD).
Turns out , the slightly warmer color is actually more accurate and attractive.
The original is too bluish.
I always put a clear screen protector on the digitizer once it's installed on the phone.
I also put a clear sticky protector sheet on the glass back.
They do not affect the clarity, though I've read maybe the matte finish ones might.
THEN, I put the iPhone 4 into a bumper case.
Many are available on Amazon for under $2 shipped, so get some.!.!
Think that covers most of what I've learned.
...oh, when I've got the screen off, I also clean/change the Home button, too!
After learning first hand how hard the iPhone 4 screens are to do, I wouldn't touch one for less than $100.
On a 3 or 3GS maybe $50, for a friend.
And no, I am NOT soliciting business!
* magnetic sheet: refrigerator magnet; flat magnetic rubber sheet around 6x8 inches