Rear main seal, crank position sensor question

I am pretty sure I have a small rear main seal leak, should have had replaced when the clutch was done a few years ago, the seal is probably original. Is a small leak ok to leave til I feel like tackling the project, looks like a fairly serious disassembly to get at it. Is there anything in there that will damaged, eg. if oil drizzles the on the crank sensor and gets dirty generally, will that cause it to give odd readings? The clutch disk I suppose could get oiled, but there is no sign of grab or any other clutch like symptom. Just wondering if a crank sensor oiling will strand me with a no start or rough start if I leave it be for a while.