Wheel wells are impossible to fix (permanently) without removing the rusted area and probably a spot twice as big as what you see. Cleaning it out and filling it with bondo will last for about 6 months before it comes back.
Look at the pics you supplied. You can see the "spider webbing" caused by rust migrating under the paint. The rust is coming through from the backside. You will notice the discoloration on some of the paint. Use a screwdriver and dig out the worst of the rust. You will see a couple of different layers of metal coming together at this joint. The problem here is the joint holds water and road salt and, everytime it rans, the water will reactivate the salt (even in the summer).
I would say, for the practice, clean out the bad spot as best as you can. Use some RustMort or converter on it and fill it with some bondo. There are fiberglass screens you can use to add strength but this area reallt doesn't require that. Sand it to contour, prime and paint as best as you can.
There are a ton of books available for this kind of work and, if you are really interested, there is money to be made in the industry...
Pick up a bodyworking book, look through it and then use some of the knowledge it will give you...
Mark