I don't personally use any glove of support, but I used to. If your coach suggests it he probably knows what is best for you and I'm guessing you already have the proper release down-pat. Master makes a glove/support, it is blue-red-black (and ugly) you see tommy delutz jr. using this. It has a metal plate in the back for support but the wrist is still semi flexible to move around. It also has a tacky rubber palm and fingers to aid in grip. Devices that will change your axis rotation, revs, etc. are the ones that look real mechanical. The cobra for example will give you more side rotation, whereas the eagle will give you more roll. When I was starting out I used a robby's. I wouldn't recomend the robby's however unless you have a problem with keeping your wrist still.
As far as getting refit it depends on the glove/support. If you go with a basic 'golf' glove style without any support in it then you won't need to be refit. If you went with something like the master glove I mentioned or like a Pro-Release by columbia then yes you would need to be refit. The glove will make your hand feel a bit smaller and you will probably have to shorten your span just a little. Your pro-shop op. isn't trying to get you to spend more money.