I think you mean the camera from the old phone needs to be transplanted if the replacement doesn’t come with the camera and other sensors out of the box.

Currently this device will still allow Touch ID to work after a screen repair, but if you try to replace the home button you will lose Touch ID functionality. It will work ONLY as a home button if you replace Touch ID.

Do step 29 before you attempt to remove the wifi

Would it make sense to use thermal compound instead?

If you use a heat gun be sure to point the heat gun away from the motherboard. After heating for 10 seconds or less use the blunt end of the metal pry tool as you don’t want to puncture the battery. You don’t need much force as after you have enough heat you will hear it unsticking when you pry at it lightly with the BLUNT end of the metal pry tool. Repeat this step on the other side. You don’t need to heat the cells near the motherboard as they are secured with small screws

You can use a heat gun to remove the adhesive. Remember you can always add more heat so don’t over do it. I put my heat gun on high for less than 10 seconds at a time

Don’t be lazy and do it right or don’t do it at all. It is not a difficult step and should not be skipped