Totally necessary, as you found, but even if you had a new home button, it wouldn’t work, because the Secure Enclave information that encrypts the storage is stored within that assembly, so if you put in a new one, you’re not getting to the storage on the device anymore.
Yeah, super light on the screws here when you put them back in. I have a bit of stage lighting right over the screw area, so I’m thinking that’s coming from being put in just a tiny bit too tightly.
+1 on the pointy knife to get the screen pried up. I couldn’t get the suction cup or tape to adhere well enough due to the glass being so shattered. I heated it for quite a while with the hair dryer on high, got a very sharp knife tip under the glass where the “notch” is, and used that to pry upward while another person slid the end of the spudger into the gap I was holding open with the knife. This one step was basically a three-handed job.
Slow and steady is the name of the game here. Heat it with a hair dryer, push the home button up through the bottom (as if you were pressing it, just a little harder), and keep heating it while you have it stretched. Eventually it will sort of snap out on one side, and then slowly work the pressure from underneath around the edge.
When replacing the ribbon cable assembly, make sure to get the “blob” correctly centered over its two pin holes. One is ringed with metal, and one isn’t. When you have the blob over the pin holes, it helps to align the connector correctly. Once the blob is in place, push back the edge of the connector facing up toward the base of the screen until it snaps into place behind a little plastic ledge just above the blob. Once that’s done, reconnecting the top cap is much simpler.
When replacing the screen, make sure to get the top (camera side) lip in first, then work downward along the sides, getting the edge with the home button in last.
After removing the glass, I'd suggest scraping off any remaining black adhesive off of the iPad's frame. Get every speck. This may be time consuming if you have lost glass integrity and have sticky, splintered shards around the edge of the frame, but you need the frame completely clean of adhesive before you put the new front panel down or else it won't lay correctly in the frame.
Definitely not for the weak of heart, especially if your screen lost all its integrity when it shattered. You'll be scraping glass splinters off the frame for an hour. Tip: Make sure to scrape off all the black adhesive from the frame of the iPad (and I mean every speck) before putting the new screen down. I apparently missed a spot, and I can't get the screen to seat perfectly within the frame (but close enough; I'm not going back in there). Also, I didn't have much luck with the microwavable tube for softening the adhesive, but I was fortunate to have a heat gun that helped quite a bit.