Pretty quick search - you were able to find the method and then show it worked in <45 minutes.
Takes most folks waaaay longer and they have multiple questions.
Nice work!
Go to: Tools >> Board >> and choose ""Arduino Duemilanove 2009/Nano w/328"..
Tools > Burn Bootloader > w/ Arduino as ISP
Yes good job. But keep in mine that you could have selected the Uno board type before the Burn Bootloader step. Benifits:
Handles watch dog timer interrupts correctly
Uploads sketches at twice the baud rate as the older nano bootloader
Smaller bootloader means a little more flash space available for larger sketches.
The only thing you have to remember is to always select the Uno board type before uploading sketches in the future, as your nano now thinks and behaves as a UNO board.