Re: fill procedure
The phillips screw (really a pin) anchors the shift yoke. If you got it back in, and the motor shifts OK, then consider yourself lucky.
To change the oil, take out both big slotted screws, let the oil drain, then pump the oil through the bottom hole until it comes out the top hole. Put the top screw in, then pull out the pump and quickly put in the bottom screw.
You do have a manual for this motor, don't you?