Man can you imagine drain plug is plugged solid. Wonder what the oil filter is doing? My bet is that the old filter has blown out or been in bypass for years!
Decompress any engine by removing the spark or glow plugs. This will unload the starter. Remember NOT to overheat the starter motor when flushing as stated in this post. Check the starter temperature by hand after you have run it for more than a minute or two. When it feels hot, let it cool off, the starter motor will thank you.
AND for those with a tow vehical and help, drag that gunked up engine around in top gear with fuel and key shut off. A quart of kerosene or diesel down the hole and a couple laps around the barnyard should bust the gunk down enough to get it to drain out.
Before you change the oil and call it good, drain the OLD filter and reinstall. Rinse the engine at lease once with a low buck light weight engine oil and partial fuel oil mix. If the rinse oil still looks like crude oil, repeat. Last but not least, a New oil filter and correct weight and amount of oil for the engine.