I went to Bad Nauheim 2 weeks ago!
It's a wonderful town, and not just cuz of Elvis. You will have a great time.
I advice you to first go to Tourist Information, it's situated on the towns main road, called "Kollonaden".
At Tourist Info you can get brochures about what Elvis places you can visit, and where to find those.
You of course want to see Hotel Grunewald at the Elvis Presley Platz, his house over in Goethestrasse 14 and the famous Burgpforte.
The barracks are in Friedberg, 4km from Bad Nauheim. When I was there everything was closed. But during Elvis week it will be open and there will be shows in the Capri club, on the barracks grounds.
Check out my profile and look at the pics I posted there.
Have fun there!!!