valve seals can be replaced without pulling the head, but it is a bit of a pain. You have to take off valve springs, retainers, etc, and also keep the valves from dropping into the cyl via air pressure in the cyl. Also a big risk of losing a keeper down in the head somewhere.
Leaking seals don't harm anything, thought he smoke is annoying. I'd say live with it until it's time to rebuild.