Minecraft: destory obsidian quickly

So I started a minecraft server two days ago so me and my friends could play, well we used obsidian to build some stuff not knowing that it is nearly impossible to destroy and now we want to destroy those structures but its too time consuming.
is there anything i can change in the server files to make obsidian easy to destroy? or a mod or something?
Answer #1
you can use mcedit and replace the obsidian with air.