I just replaced my gasket. Yeah, there is a gasket. I got mine from the local Honda shop. Pretty pricey for a lousy gasket though. I used sealant on both sides.
So, I guess I should note that I'm not a guru and I'm talking my 750 and I have no idea what bike you are talking about and if all SOHC/4 bikes are all the same.
The shifter and sprocket covers are seperate. The sprocket cover is open and doesn't require a gasket.