I've just rebuilt my calipers using the W&N kit, although I expect the contents are much the same.
I also took the advice not to split calipers, which I didnt. Once bores and pistons cleaned off, installing the piston o ring was no problem. Similarly the dust bellows went staight on but I had real problems with the metal split ring that holds dust covers in place. They are way too tight and as I tried to work them around, often the "first" end would pop off and risk damaging the bellow. In the end I had to slightly stretch and deform them before working around then squeezing back together.
So a bit of a fiddle but worth it !
Rich