Received my screen yesterday and I installed it last night.
The only bit that I found a bit tricky was unclipping the metal bracket that holds the focusing screen in place.
Once I had gently fiddled with some tweezers (supplied by focusingscreens.com with the order) for a while I got the clip unhooked and it was easy from then on.
I managed to avoid scratching either screen, although got a small fragment of hair on the inside of the K3 screen... Not a big deal and I had some dust on my stock screen anyway.
I used one of the thin plastic shims supplied with the kit. Focusing is spot on as far as I can tell...
Haven't used the screen much yet but I would recommend it, I'm happy
Thanks for all the help given earlier in this thread.
cheers,