heehee... exactly my friend! Its best to take care of these things early... and indeed 'its just pvc'. Really quite wonderful how cheap it is that experimenting with various plumbing endeavors is cheap enough
As for gate valves... have you looked on the reeeeeeally high shelves at Home Depot? They do stock a couple sizes of gate valves (I have seen them in several cities/states beside my own). But if local is not available... no worries, any of a number of places can ship you one with a good 'ol google search