IF it is the small cover under the distributor it is about 2 hours work max.
If the main cover is leaking it will take much longer. Both cases no special tools needed, only for the fan you will have to make a tool (very easy) because there is not enough room for normal tools.

There are lots of very good sealants.

Dealers charge way to much for these repairs. I once had a oil leak in my old 280S, the dealer estimated a 2000$ repair, our independed shop (who unfortunately retired) fixed it for 150$. It nerver leaked again for the remaining 150.000 miles.