Welcome to the site and congratulations on making an excellent choice of bike.
Worth checking the sprocket nut and cleaning out all the muck that is likely to be inside the sprocket cover while you have it off. The problem only effected a batch of bikes earlier than yours with under size shafts or others where the nut hadn't been fitted correctly. i.e. clean nut and shaft, loctite and correct torque.
Hugger well worth fitting but be aware when getting one that the earlier FZS600 (boxeye models) have a slightly different fitting position on the swinging arm, so you need the correct fittings for your bike.
The manual recommends that valve clearances should be checked every 24,000 miles but rarely need altering at that mileage. Engine oil and filter change unless you are absolutely certain it has been done very recently.
Fender extender again a good mod as the front mudguard is useless for keeping road filth and bits of stones off the engine and exhaust pipes etc. I went a stage further and fitted an aluminium shield to the front of the exhaust pipes, as in this photo if you can see it. It started off polished but now looks like it has been shot blasted. Not to everybody's taste but it stops a lot of the spray and other stuff hitting the front of the bike.
Good luck and be extra careful while you get used to the new bike.