I have a 1975 Sears Ted Williams (Eska) 5.5 (mod.# = 217.58571.0) and the motor is a Tecumseh (mod.# = T643-20B). I am wondering about changing the oil, i see the drain plug but where do i refill at and how much do i put in, also what wheight oil should i use? any help would be great thanks. (...