Well hate to say this but if it die while running you probably toasted the engine. Without oil the aluminum starts to overheat, melt, and transfer to steel moving especially the rod to crankshaft journal leading to the rod breaking; sometimes sending it thru the crankcase. Since the engine has ran without oil a tear down is in order to check the rod/crankshaft journal for this transfer. Once this transfer starts it only gets worse unless cleaned and repaired. If it is there then a new rod needs installing and the crankshaft needs cleaning.
As for the oil plug as Dieselboy said it is a taper (pipe) thread. Now new plugs do come with red Loctite type sealer but I would not use it after the initial coating is worn off as I have seen it to seize completely preventing plug removal. I had a Cat pressure pump that I was rebuilding and the service manual spec'd it on the check valve plug caps. It seized before I seated the cap and I almost didn't did the cap back off. It using a die grinder to re-cut a new hex on the cap even me using a torch to heat the joint.
Those tanks are HDPE plastic and welding it is the only method that works permanently. NO open flame or sparks permitted as explosion is possible. Here I use a soldering iron with all the solder removed and the same HDPE plastic as a filler material. This is after the tank is thoroughly cleaner and dried. The reason I use a soldering iron as I can get very deep welds where the hot air method only penetrates slightly leading fairly quick failures.
Still the best option is replacement and by no way I recommend anyone doing this type of repair without the needed experience or supervision.
As for changing the oil in these small engines I have changed over to using an pneumatic (air operated) vacuum oil extractor. This was mainly because I was getting in engines without drain plugs or they were inaccessible. Not easy turn garden tillers on their side or upside down. There is added benefit for me as it is a lot less messy plus I can easily fill jugs to take the recycling drop point while I am grocery shopping on the weekends. I guilty of having slip an new engine 90 degrees making the plug inaccessible myself as there was no way adding an access point.
