Download the proper Yamaha Service Manual towards the bottom of that page. All torque specs are listed in the doc along with a lot of other useful information. I believe the torque specs for the bolts, crankcase M6, you're asking about are 7.2 ft lbs (10 Nm) and you want to make sure you're using a lower range torque wrench, 1/4" would be best. Aluminum crankcase with steel M6 bolts are easy to strip threads if you have an out of spec torque wrench or large torque wrench that doesn't work well for low range.
Yes you can do it. Clean and replace the gasket but you should also consider using some liquid gasket (Yamalube - Yamabond #4 Adhesive) spread around thinly to hold the gasket in place. Use the Yamabond liberally where the stator wire set exits the crankcase cover as that can be prone to leak.
@Dgiginabigrig.....As RR posted above it is an easy repair.
You will need to drain the oil.
Installing the cover can be a little daunting because of the magnets in the rotor. A socket that fits the crankshaft nut that holds the rotor on will allow you to slide the cover on easily without pinching your fingers.