Start by putting his litter box on top of the toilet. Once he is OK with that, get a disposable foil turky roaster and fill it with a bit of litter and put it in on the toilet, fitting it perfectly so there is no chance of him stepping in it and making it fall in. Taking the top toilet "seat" and lifting it up and putting the foil roaster under it so that it clamps down on it might be a good idea. Once he is OK with this, start by making a little hole, and gradualy increasing the size in the pan. Each hole you make should only be made after he is comfortable with the new "thing" he has to go to the bathroom in. After the whole pan has been cut out, leave it like that until he gets used to it, and then take the pan out.
Flushing: No idea
This should take a while, but in time he'll probably be able to do it.