Well DJDPilot I am preusuming you all ready have the World of Minecraft Game client but if you don't you need to install it, But anyway when you are on a level there should be a button on the left hand side in between the 'exit' and 'screen shot' button, You just click that and it will make a level dump and then there should be a file in you World of Minecraft folder called 'Level Dump' or somthing along those lines, So it is simple i'll re expain it bellow here for you!

1. Enter Multiplayer Game VIA World of Minecraft Game Client
2. Go to the level that you wish to 'Dump'
3. Press the 'Dump' Button on the left hand side
4. Go into your World of Minecraft folder

And there is your level dump! :D