Voxel Sniper help?

I used stone to build a mountain range, how would I change the stone to dirt? Is there a replacing command?

 

I recommend using Worldedit for this kind of thing. If you want to replace only the top layer, you can use /b over d1 and then /v dirt.

 

You can use the modifiers that /b supplies you with. After /b [brush], there are an optional 3 symbols you can add. The first two are what you will be painting (in this case a material "m") and what you will be painting over ("m" again"), so you would type in /b ball mm to replace a block with another block in a ball shape. Then simply type in /vr 1 to signal that you only want to replace stone and /v 3 to signal you want to replace it with dirt.

EDIT: You can read more here:
http://www.voxelwiki.com/minecraft/VoxelSniper#Performers