Press the shrader valve on the fuel rail under the plastic cap to relieve the pressure (into a rag).
Turn the locking ring counter clockwise with a flat bladed screwdriver and gently tap it around with a hammer. GENTLY. It'll only go about 10° before it unlocks. Be careful of dirt and debris. Do NOT vacuum it up or you may explode.
I taped UNDERNEATH the opening to make it not go in there, then blew the dirt out with a can of air.
You will need a new tank seal.