It's quite easy in itself but one channel took all the force out of me to snap into place; the other was a breeze. The plastic just isn't molded to perfection so I can't really tell you what to expect (but yeah it's just a matter of snapping out the clip and snapping in the cup into the headband).
Just a word of warning:
I hope you're not putting too much money because you might be (maybe) slightly thrown off by the comfort. Even on my “swiveling type” headband I have one single hotspot (fit isn't good; the horizontal plane angling of the cups is too small compared to my ear's) and while it works awesome and I'm not feeling it for an hour or two, after that I have to insert a HD414 pad onto the stock sponge of the KSC75 just to make them bearable.
I swear it may sound unimportant, it's just foam but the added pressure (which gives you bass, it's a desirable aspect and added benefit you can only have with this headband) get's very irritating in long sessions... just like some people complain about the scratchy Grado headphones foam pads: when you don't have a minimum of comfort, it's hard to listen no matter the headphone.
But you can also expect comfort to be fair overall (or else you find a way to increase cushioning like I do myself with a pair of HD414 pads) and still a lot better than that of the clips. You might also have better results if the non “swiveling headband” happens to be better designed. This also all depends a lot on the morphology of your ear.
Well, I am not expecting huge things from this cheap cans, I am using them in gym and it keeps me happy, however the clip system is painful, hurting my ears also I don't feel comfortable, they feel like "just about to fall". So I can spend a few euros more to keep them, otherwise I will stop with them and order PX100-II or something.
So KSC75 will not be my main headphone (I have a totl ciem for that but I am not risking it in the gym ). So I am not willing to put a fortune on them or expect the sound and comfort of HD800. I hope with that headband thing, it will be good enough to keep. Will post the impressions as soon as I am done.