CV axle fused to wheel hub?

That's correct, forgot this was the front shaft. For that you unscrew the retainer then the seal can be removed, If you are careful you won't disturb the bearings. Replace the seal and put it back together. Tighten the ring down and put it back in the same place as you removed it. The locking tab that bolts to the housing usually leaves a nice spot to return it to or you can just put a mark on them before you remove them. You could get a heli-coil kit to rethread the hole. It's probably at the right size for that. Or epoxy a stud in the hole and just use a nut on the outside.