It is not really necessary that the holes where the plugs go be completely clean and dry. You can wait until you are replacing the valve cover gasket to clean them well. They will be more accessible then.
If there was a lot of oil in those holes, it ran down into the cylinders. It would be wise to crank the engine while the plugs are out to blow out any excess liquid so it does not damage the engine when you crank it.
You should clean or replace the rubber boots that attach to the coils and fit over the plugs. Something like aerosol carb cleaner and a rag would clean them. If you use that, wear rubber gloves.