Help me start over

This is my first time trying to mine some RVN for fun. When I set up a qt-wallet, the software must have asked me to memorize a passphrase. I didn't pay attention as I didn't understand the implications, so now, while my wallet shows (a measly) 16 RVNs, looks like I have no way of using/sending, etc.

I would like to start over but I am not quite sure how to completely reset the wallet. When I uninstall it and reinstall it, it brings back my old wallet with the balance showing.

How do I start with a fresh new wallet? Also, could someone please explain the concept behind the "receiving" address and "wallet' itself? My initial thought was that they were the same thing.

Why would one use 1 address for receiving and 1 address as mining? Wouldn't you incur fees to transfer to yourself to another receiving address? confused.