Do I truly NEED a bridge or implant on molar #30 and a new crown behind it? (photo)

Hi, thanks for sending your question. I am sorry but your xray is not of diagnostic quality. I highly recommend to you seek a second opinion with another provider who can perform a comprehensive examination of the area and the xrays and give you his diagnosis. All the best.

Unfortunately your xray is very poor quality and not diagnostic. If you have concerns about the treatment suggested by your dentist it is always possible to get a second opinion. 

Since the provided x-ray isn't helpful, I can only speak in generalities.  When root canal treated teeth fail, most of the time the next step is removal. A bridge can be a great option, as is an implant.  If the adjacent teeth had NO work done at ALL, I would suggest the implant, but the adjacent teeth have crowns.  You state "perfectly healthy teeth" but you are incorrect.  The nerves are not dead, but the enamel is gone (from having crowns).  To do a bridge, simply remove the old crowns and make a new restoration (the bridge).