For me, the hardest parts were:
*Getting the screen off with the suction cup
-You definitely need some force to get this baby off, but not too much to damage the phone. The first time I did it, the whole screen came off at once. My heart sank a bit, considering I didn't need to use the plastic tool almost at all to get the screen off, but, thankfully, I didn't damage the ribbon cables.
*Prying the battery away from the logic board
-This is worse than getting the front display off since the battery is literally glued to the inside of the phone. I did a little bit of prying with the plastic tool (in the three designated prying spots), but stopped after fearing I'd damage the logic board. Instead, I pulled on the plastic tab that says "Authorized Service Provider Only" just enough until I could use the plastic tool more. After I lifted the battery up enough, I just used my fingers to pull it out from the phone.
*Putting the tiny screws back in
-Not necessarily the hardest, but definitely the most frustrating.
