Hey, nice start. You're on the right path with your terrain textures, and making tiling textures. Once thing it seems like you maybe aren't getting, though, is blending terrain textures together. If you know how to use masks in photoshop then you've already got the basics. Blending two terrain textures is done by using a…
Good luck with the project :D Do you plan on rendering everything in Maya? Why not put it into a game engine? Always a good skill to be able to show your assets in-engine, and now that for example unreal 4 is free... Also, I can highly recommend this tutorial by Jamin Shoulet for texturing, not 100% sure but I think he…
Do you want to keep it all in Maya? Usually it's easier (at least for me) to do the terrain in the actual game engine you choose to use, such as UE4, UDK, Cryengine, or Unity. (And all of these are free now, woo woo!) All of these support landscape height-map painting which is pretty easy to sculpt out with in the actual…