There's a lot of tools out there that can make life easy for terraforming. I would highly suggest looking up how to use brushes for WorldEdit, then go about installing SPC and using it. Be aware, though, WorldEdit works about 20x better when used on a server.
On top of that, McEdit can be helpful for really really big cuboid-ish stuff that you need to get done, but WorldEdit can do that in-game, so it's not really necessary and can be kind of redundant.
Finally, I might suggest going to teh googlez. There's a few sooper shecrut tools that can be super awesome helpful if you know where to find them and how to use them.