Yeah & pray that it is the o-ring leaking, because changing that oil seal on the crank is a 'split the cases' job. The oil seal has a ridge on it & it can't just be pushed in.
+1. A lengthy repair for such a small issue.

As a bandaid repair...you might want to remove the points plate, clean that seal/case area really well, (degreaser, acetone, etc.) and apply a thin smear of a non-hardening sealant around the outer edge crank seal/case. Might just do it.
Its out of sight and no one but you will know
