Consulting a dentist to remove tooth decay

Hello all,
My son who loves chocolates is suffering from tooth decay. I brush him twice a day. But I don’t know why he is having tooth decay. I guess I shouldn’t have let him have chocolates every day. I tried many home remedies- some worked, some didn’t. But it gave only temporary relief. When I discussed this with my friend, she suggested undergoing tooth extraction treatment from a nearby dental consultation in Waterloo. As per her instruction, I took the appointment with the dentist over there. The dentist suggested for taking the digital dental x rays. After the examination, he advised for tooth extraction in the next appointment.
I want to know if this procedure is going to be painful to my son? What are the things I should take care of before tooth extraction? Can someone please share your views?
Thank you in advance!