Better bet is Lindau- Oberstaufen-Immenstadt-Oberstdorf- Lech - Arlberg pass- landeck- imst- garmish- Wallgau- kreuth- Tegernsee- Schliersee- Bayischzell- Tatzelwurmstrasse- to Oberaudorf and then picking up the route for the run down to Berchtesgarden
Great, now someone's found you the road, it's a real chance for you to play about in the Garmin software (and with your GPS device) to find out how they work. You'll learn a lot more than being spoon fed everything. The best thing? You really cannot break it