So, to close this thread, I unscrewed the hose leading to the coolant thermostat and reached in to the left side, and felt the water pump. The plastic impellar blade was definitely split in half. I ordered the timing belt, water pump w/metal impellar blade, & tensioner from ebay for $120. Then I got my auto-mechanic to install the new parts for $300. I initially tried to do it myself using the following DIYs:
VWvortex Forums: DIY: Transverse Timing Belt, water pump, thermostat...
VWvortex Forums: DIY: Timing Belt And Coolant Pump Replacement on 2.0 AEG! Pics Inside!
BTW, you don't really need brand new engine mount bolts. My mechanic scoffed at me when I handed him the new bolts that I had bought from the dealership for $30 (4 bolts). To be honest, if I didn't hand him the G12, he probably wouldn't have used that either. I guess in a car with 105k miles, G12 or Dex-cool or whatever, they're all the same?
Anyways, I've attached a picture of the broken impellar blade.
Everything is running fine now. Heat again. No overheating. Everything good...for now. Appreciate all of the help.