I just finished doing this without any special tools, the circlips can be
removed with snap ring pliers or a small set of needle nose pliers. It is a
really good idea to shove rags around the piston bases so that errant parts
don't zing off into the interior of the engine. I found the wrist pins very
difficult to remove. The Haynes manual suggested making up a hook out of
wire to gently pull them out FORGET IT. You don't want to pull too hard
sideways anyway so here is what I did. Get a piece of aluminum tube that has
an ID large enough to allow the wrist pin to fit inside and an OD small
enough to fit through the access openings in the case ie the water pump
hole. Then get a threaded rod of 5/16 inch diameter and a selection of
washers and a couple of nuts. Now the pipe goes through the access hole and
rests against the piston side and the threaded rod goes through the pipe and
through the wrist pin so that you can attach a nut and washer slightly
smaller that the inside of the opposite circlip which you can leave in
place. Now what you need to do at the free end is put on a large washer  and
nut so that you can crank down on the nut against the tube which will pull
the wrist pin out of the piston and into the tube. Be careful as the pin is
trying to get into the tube since it will hang up on the sides a bit and
might need repositioning of the tube. Once you get everything lined up it
works pretty well. I don't know  why mine were so hard to pull but they were
varnished up a bit.
Does anyone have any ideas about how to clean them up so they will go back
in a bit easier?

Good luck

Tony