Don't pay attention to Nooby, he is the resident Hybrid Hater.
Problem is, though, he usually makes good points.
I think the Hybrid battery warranty is 8 years or it might be the same 10 years, 100,000 miles as the power train.
Either way, the Touareg Hybrid is a kick ass car, but like Nooby has pointed out in other threads, it's technology is dated. It really needs a bigger battery and bigger electric motor and plug in abilities. (Like cousin Cayenne received recently.)
Most of us have had growing pain issues regarding the Hybrid specific components and no major issues with the motor. Like you mentioned, the motor is a fairly normal engine for Audi vehicles and has good reliability or they would have dumped it a long time ago. My biggest issue with the motor is helping VW techs figure out how to work on an Audi engine that they have never seen.
As for residual value, many people may not be as vigilant as you are regarding the past of the vehicle. I assume it has a clean title, but you just caught the replacement in the CarFax? Most people check the CarFax and if all the little green arrows are checked then they are happy.
Good luck and let us know how you make out.