Most likely they will test for u on the spot. Then if all okay, u bring back. But if gt any leaks when u r at home, they may push it to you.
Best to DIY it. Can save on parts and gain the experience. Can learn from youtube which i did. Watercooling is not only about doing and showcasing but also gaining the experience and learn how it works. Maintenance will also need to be done by you.
Anyway, i dun think aftershock will do wc on your pc. If needed, you have to buy their pc w/ wc.