Look in the lower left corner at the 1/8" input. You can plug anything you want into that, but it won't charge.
Or, if you already have the stock head unit, there is also an older $56 adaptor (PIE CHRY02-AUX) on eBay that plugs into the CD changer port. The seller lets you choose between iPod, aux, or Zune rca cables. You have to tap the iPod cable into a power source if you want it to charge while playing. I routed the cable to come out the lower left of the glove box.
The only issue is that the iPod cable is the older FireWire style. It needs a crossover adaptor for the newer models to work. I added a dock extender cable to the crossover to keep the bulkiness hidden behind the dashboard.
In the end, this is only a little less expensive than the head unit you linked to, but you only have one cable for the iPod rather than two if you want to charge it.