Next Round Is On Me
I agree with @billfort , do both diaphragms at once for a more even sound base. They will send you your old ones back with your speakers if you ask them to. You can keep or sell the single good diaphragm or keep it as a backup. I still have mine.GPA diaphragms are up to $148 each. I'll certainly look into repairing the voicecoil lead.
If it comes to the worst, the $148 diaphragm cost makes the complete overhaul look downright affordable.