You access the distributor from inside the cabin by removing the interior panel. Removing the decklid won't give you anymore access then you already have.
You have not indicated what ignition system you are running. It sounds suspiciously like an MSD, aka, "might suddenly die"
It could also be as simple as one of the cap retaining clips popped off.
I've got Webers too. You need to climb in the engine compartment, lay across the headers, to reach the distributor but you really can't service it from there, just check to see if the cap is still on right.