You should use wifi for internet and file sharing, it is so much faster. For wifi sharing to the MBP (I posted this in another thread)
Open SYSTEM PREFERENCES -> SHARING
In SHARING, you need to turn on INTERNET SHARING. Once turned on, on the right, you need to set SHARE YOUR CONNECTION FROM:-ETHERNET-, and then in the TO COMPUTERS USING: dialog, check airport. Once done, click the AIRPORT icon on the menu bar, and CREATE NETWORK. It will prompt you to name the network, and give an option for a password. You can leave the default channel alone. Once done, tell your MBP to connect to the wireless network you just made.
Now for File Sharing, in that same SHARING menu, you need to turn on FILE SHARING. Now for example, you want to access files on the mini from the mbp. Enable sharing on the mini. Then on the MBP, open a finder window, and you should see your mini on the side. Click it, and then in the upper-right of the Finder Window, click CONNECT AS. In the dialog, type in the username and the password for the mini. Now you can access all of the mini's files from the mbp with read and write capability. And you can do the reverse to to access MBP files from the mini.
