Just wanted to give a brief update with my experience with Walmart Wireless.
Overall, it went quite well. I ended up calling their 'order by phone' number instead of doing it online. I have a family account and wanted to make sure this upgrade didn't affect my second line.
Once I placed my order, I was able to track the status online. My SG3 was shipped and delivered on time. Once I received it, I used the same online status tracking to activate the new device. I actually encountered an issue and had to contact Walmart Wireless - I used their online chat feature. Within about 10 minutes, they had my device activated.
I checked my account online via Sprint.com and confirmed that my second line was not affected, my bill was the same and my new phone was activated.
All-in-all, my experience was great - $80 off retail, no tax, free shipping.