Google is your friend, my friend :P
EDIT: if you're using windows 7, to get to a map, the path is..
C: --> Users --> your name (or whatever you use for your username) --> AppData --> Roaming
Note that the name of the folder is .minecraft, so you can take the lazy way out and just do a search for it on your computer.
Your single-player maps are in the Saves folder.
To upload it to the internet... well you gotta go to a site that allows you to upload stuff.
That is freaking sweet! Well done completing it!
Moderator of Heroes of the Storm, come say hi!
its kind of cheating, but it is pretty cool :P
I know people who build things like this just by dropping tons of sand.
My Radio Broadcast: http://grooveshark.com/#!/dookleto/broadcast feel free to come and listen