I just used the instructions that came with it.
Very easy if the old one comes off without a fight. Pain in the arse if it doesn't.
Undo clip & remove selector cable, undo nut & remove old shifter thingy*, fit pin to new shifter thingy, fit new shifter thingy (making sure sliding thingy is in sliding thingy slot), tighten nut, refit selector cable, test drive and enjoy.
*If old selector thingy in difficult to remove then lift it up as far as it will go, pack to underside, replace nut loosely and tap nut with hammer. Repeat with increasing amounts of force until shifter thingy comes off shaft.
AS you can tell I don't write alot of guides