Yeah there's an o-ring around the dizzy shaft, I've had one leak befor. $0.50 and half an hour and it was fixed. :D Just don't put the dizzy back in 180o out.
Elec dizzies go for anywhere between $50 and $200 depending on condition, there's one on ebay at the moment.
Either type with do (internal/external ignitor) as long as you use the correct coil/ignitor.