You can get some washers to cover the hole with the switch, as long as you aren't too worried about the look. If you find decent looking washers, I don't think they look that bad.
On the knobs, an easy way is to get a twin strand wire (like a bell or speaker wire), and split it in the middle and push one wire under one side of the knob and the other under the other side. You should be able to get them off with that. Another approach is to use a spoon as a lever, but you need to protect the body when you do that. One last thing, I'm assuming that these are push on knobs. Just check that they don't have a screw locking them onto the shaft!