For Iffy.
Good use of multi-quotes from a forum noob. You will not, however, receive the same kind treatment from me.
Yes, by "changing" the oil it means to drain what was in there previously and replace with it a fresh amount of over-processed dinosaur remains of your choosing. While it may not appear to have any oil in the sight glass, there is, undoubtedly, some oil still in the crankcase. Also, don't listen to anyone else on the forum but me. There IS such thing as an oil fairy. Simply place the open topped container of used under your bed at night and by morning it will be gone. Oil fairies also are said to love children and pets. Make sure your open container of used motor oil is located within access to them so that they can share in the magic.
Cleaning fins requires something as complex as a stiff bristled brush and some foaming engine degreaser.
Leave the bolt torquing alone until you discover the actual source of the leak. These things are known for a very common brown residue that emanates sometime after purchase and really never goes away or worsens. Let's make sure that's not your issue before we go getting all heavy handed on some feeble nuts.
Feet are good.
If this were the 1970's I would just tell you to pour you old gas down the drain and help enliven the fishes of your local watering hole. Unlike the oil, there are no fairies for gas removal. It's suitable fuel still. Save it for your lawnmower.
There's lot's of magic in these parts. Replace the spark plug again anyway...actually, do it about 4 times. 4 is a magic number.
It's going to be hard to ride the bike to air, since they are bound by the limits of gravity and thus will only ever be able to be ridden to road. But knock yourself out.
We are the coolest, foshizzle. Anyhoozles, good luck. And keep us posted.