All you need to do (if the engine is still capable of running) is flush and drain the coolant, drain the old oil and replace with fresh for the wait period. When you rebuild you'll be cleaning and relubing with assembly grease anyway. Depending on the extent of the rebuild, if you're not going to touch the pistons/rings, then make sure you seal the spark plug holes, intake and exhaust ports to prevent stuff from getting into the combustion chamber.