Most of the time, the root canal is done first, then the crown is redone. This prevents you from drilling thru a new crown that will posibly lead to porcelain fracture or micro leakage in the future. I'm not sure why your endodontist would want to do it like this. He is correct in wanting the old crowns out and the decay removed. But if he wants it done prior to the root canal, your dentist can put you in a temporary crown that your endodontist can remove to complete your root canal. This would allow him better access and would avoid senseless destruction of your new crown.
Without seeing an x-ray, I can't tell you for sure if you need a CL or not, but I'd think that if 2 professionals agreed that it was necessary, then you probably need one. A CL is needed because we need a certain amount (about 2 mm) of space between where we end our crown and where you're bone begins. As for who should do it, I would go with an Oral surgeon or Periodontist first.
It only has to be done if the tooth needs it. Some reasons would be: If the tooth has a large cavity and it is into the nerve or if the tooth has broken and there is not enough tooth structure to place a crown onto it.
You could visit a specialist (an oral surgeon) but I don't think there is going to be anything they can do for you. Nerve damage can happen when an impacted wisom tooth is removed, as I'm sure you were told. Time can heal the nreve but sometimes if the damage is too great, the nerve may never recover. For you it will continue to be a waiting game. Good luck.
You can keep the bonding on since a root canal on a front tooth is done from the back, and would not disturb the bonding in the front. However, I would not recommend this. The crowns, while looking better will offer your tooth better support and will help prevent the tooth from further fractures.
