just to make sure, I am putting the Superuser-3.0.7-efgh-signed.zip file into sdcard2, correct?
This is where I'm getting kinda confused because... I'm still not sure which directory is the phone's "real" root folder. Before, I thought it was the /mnt/sdcard :'(
Any clarification would be appreciated

& thanks in advance! You're truly awesome, Scotty
edit: Just more clarification. I was able to get root access (according to all the root-only apps + that root checker app). So now all I want to do is do a nandroid backup (via Amon Ra - followed this guide to a T via the TEMP Recovery method) but for some reason I can't go into the Recovery mode. I'm getting the hboot screen, just that I get stuck/hung up on the screen with that red exclamation point. So... I'm starting the process from step 2). Figured it could be me putting that Superuser-3.0.7-efgh-signed.zip in the wrong place/folder.