My friend Peter dropped his iPhone 6s in a parking lot. The poor thing landed front-side down on a speed bump. Ouch! Thankfully, no sensitive parts were broken so it was technically usable...if he wanted to keep it in a plastic bag for the rest of his life.
Peter had just helped me move to my new apartment a few weeks ago, even being on call at the last minute to move my last bits to my new place. It was a fitting thank you to be able to offer my skills to repair this for him.
I've repaired my iPhone 4 before, and thought this would be similar. Boy was I wrong. First off, with a shattered screen the little suction cup didn't want to hold on to anything. And then the replacement parts needed the home button and the camera reattached from the old phone. Taking things apart was tedious, but not terribly difficult. Re-assembly however, stretched on and on as I had to reassemble the camera and speaker assembly five different times to ensure the pieces would fit properly. But, patience, perseverance, and tenacity always wins against stubborn tech!
1). If your screen is cracked and you can't get the suction cups to hold their suck, don't be afraid to bend up the screen a bit (it's going to anyway). Remember, you're replacing it, so if it starts to come up and shatter, just remove the pieces from your workspace and keep going. I actually ended up having to pry the bottom of the screen up around the home button very very VERY carefully just to get underneath the bottom. Be patient and you will win.
2). Camera reassembly/reattachment: this proved to be the most challenging part of the repair. There are sensors folded under each other, pieces that fit into tiny little sockets, connections that can't be touched, and a holding clasp that all has to be carefully held in place. Be patient! And don't force anything that won't go. It all came apart, so it will go back together. Eventually.
3). Laying a piece of double-sided tape on the table to arrange screws in order of disassembly is a great help, especially when working with a series of screws that are different lengths.