Forget about a leftover, there's no such thing as an '08 TDI in NA. The '09 is the newest version of the TDI, dispalcement is increased to 2.0l in the Jetta, it now has common rail injection, and meets 2010 emissions regs through the use of DPF's. I've been driving a Jetta TDI for last several years and wouldn't trade it for anything. That said, I wouldn't buy a new one since I wouldn't buy the first model year of ANY major design change. You said this is a commuter for your wife, is she the kind of girl who doesn't mind fueling at a typical dirty diesel pump, and will she pour additive in the tank so the fuel won't gel? And you can forget about using bio-diesel in any concentration greater than 5% also. Go here for lots more info...
Fred's TDI Page. TDIClub.com. VW TDI Enthusiast Community. And good luck.