Terrain Trouble

I begin today experimenting with Unity's terrain creator. Appearently Unity is built so you can easily create complex terrains within a short amount of time. I spend a lot of time making a mountain range that curves around in a bowl shape.
I go to the Game tab to see how it works, and see I didn't add lights to the scene. I do a little research, and add a lightbulb-style light to the scene.
I am still disatisfied with the gray texture the terrain has. I do some more research and add a rocky texture to the terrain. I don't even know if i am even going to use this terrain in the game, but it looks really cool. A lot cooler than gray.
I add more detail to the terrain, then I try to add trees, then Unity crashes. I lost all of that data so I'll have to start over. But I still feel satisfied learning all of the stuff I need to make terrain.