Success... I followed all of this by the book. and was able to leisurely find my NUMEROUS odd points after upgrading/patching the test site, even did live purchases during my testing phase on the test site. All the pages I modified in 2009 were a little work to dig up, but I found all of my notes and banged it out in short order.
Just upgraded my customers live site, then pushed my modified pages up, and have now checked everything out (made live purchases).... Good to go!
Thanks to Alex & Kelvyn!