Oil and filter is definitely optional as there are pluses and minuses for when. Change in Fall you could get a little water in oil pan from condensation (think dipstick tube) from humidity and temps going up and down all winter season. Change first thing in spring and all the sediment that has settled over the winter will be tougher to extract. My experience is that these are minor considerations and it really does not matter much as long as you hit your 50 hour mark.

Most important thing is getting water out of block, manifold, lines and pumps if temps get below freezing for a prolonged time. The other stuff is solid advice, but will not cost you $1000s for a missed step.