81 308 distributor end o-ring replacement?

I have a oil leak coming from my distibutor for some time. I have replaced gasket and cam seal still a leak. There is a small metal plug at the end of cam under the rotor that looks good. So I think I need to replace the o-ring. How hard is it to take out the pin with the cam in the car. It is leaking to much to leave alone. I have had the car for over a year now and have done alot of work to it,but this leak is killing me. Any help would be great.
thamks Jim