The other gasket you will probably not need, unless you take the two halves apart (you don't need to to remove the unit). I recently replaced that gasket on my dragbike motor. While you are at it, you might want to order the 2 o-rings that fit on the oil tube: SKU: 93210-06667-00
O-RING I know they were pretty deformed in my motor... not sure if it is needed or not, but might as well while you are in there. I really shouldn't be the one giving you advice on this as I am really new to these engines, so if someone else has some input, please speak up.
Jeff