After research, I've decided to go with the Gutmann method of a wipe using Darik's Boot and Nuke. I won't be able to do the wipe for a few days (friend's drive), but I'm hoping all goes well. My second question still applies, as I would like to try to mine data before and after the wipe, to see the results.
Here is the link to Darik's Boot and Nuke if anyone else was interested:
Darik's Boot and Nuke (Hard Drive Disk Wipe)