Oh just forget about the worries, you'll have a Sniper case with a fan knob to turn when you get bored, just look at that thing, I'ma turn it and go "Weeeee" as soon as it comes through my door.
if your being such a worrying soo much then consider the raven case with the special layout. rather than it more likely (if it ever happens) leak on the gpu, it will morely leak on the bottom Air Penetrator fans.
you should be fine to do that. not sure on the screw mounting as some tends to be the standard bulky fan screws where the one supplied with the case are small thin screws. you could perhaps swap the screws over i believe?
