Is it possible to lose the Top Nav from an individual page?
Using Jamroom
This isn't doable via point-and-click unfortunately, you'd need to to use an SFTP tool to connect to your server and upload a text file into the skins directory. Which would mean looking at code.
If you uploaded a text file with the name avacardo.tpl and it contained this:
Hello world
Then when you visited yoursite.com/avacardo you would see "Hello World".
Once its created you will see it as adjustable from ACP -> SKINS -> YOUR SKIN -> TEMPLATES -> avacardo.tpl -> MODIFY