Both my husband and I had old phones that needed new screens because they cracked.
We decided that we would turn our old phones into family phones for times that our kids were going to be away from us and communication would be important. Knowing this motivated our 14 year old son to fix them because he and his brother were going to Washington DC without us. My son researched iFixit and determined it was the most reliable website to order a repair kit from. After we ordered it, he promptly took it into his own hands to repair the broken fronts of our phones. He was able to do the job with the detailed videos and now he is a happy camper ... and so is his brother.
My son took an egg carton and labeled the holes as he came to a part that needed to come off. He put the part in the hole so as he put it back together, reassembling was a breeze. You could use a muffin tin too.