Not built in, but it is an option. Just need to purchase the HGE-100 wired handsfree with remote control and built in GPS. It plugs in like the stock headset, is about the same size as the remote for the iPod, and retails for a hundred bucks, although you can find it on ebay and Amazon for less.
If thats not your cup of tea, I use a wireless bluetooth gps module with my W580i. I picked it up for 50 bucks on ebay, and it works great with google maps and a couple other free compatible programs.