You will need something to pry the two wheels apart. I've found that using two pry bars work best but you might be able to accomplish the same thing using (2) large screwdrivers with an object between them as a fulcrum.

The WD-40 is a general purpose lubricant but any light oil can be used. Some people feel you shouldn't use oil at all but use graphite in lieu of oil.

The clamp will make reassembly easier but you might be able to do the same thing with a hammer or just your foot.