Ive never used the close contact but my friend who is big into showjumping has one and loves it.
Yes, they are fairly hardy. Mine are both pretty old but structually still as good as new.
They are a little fiddly to change until you get used to it. I could nearly do it with my eyes closed now :P They do come with step by step picture instructions tho
As for measuring, well this depends on how knowladgable your tack store is, but this is what I do. Take a wire coat hanger, and mould it over the horses wither at the place werre the gullet will sit. Take it to the store and say 'this is my horses wither, I need a gullet to fit'