Just got this to work. Posting my steps here for reference. Happy Switching.
Quick summary: use feature phone line to get subsidized iPhone5. use iPhone5 on smartphone line to keep unlimited data.
Note: feature phone line does not have any data, just has 9.99 line access fee.
1. Use the feature phone line that has upgrade available to order an iPhone5.
2. Received iPhone5. Turn off the feature phone. Activate on the feature line. Takes about 10 minutes.
3. Turn off iPhone3. Login into verizonwireless to re-activate the feature phone back on the feature phone line. Enter the SN underneath the battery. Remove the 30 dollar for 2gb line as part of the activation. Feature phone now works as normal.
4. Go into the verizon store saying that I want to activate an used iPhone5 on an existing smartphone line. Need a new nano sim card (free of charge from verizon store) since used iPhone5 has one locked. Service rep takes about 20 minutes for the process. Confirmed that it will keep the unlimited data.
Hope this helps.