Is there any possible way to toggle between a cd and the map without changing cd's

When you remove the Nav DVD, it goes into memory mode. It will cache surrounding map info and display that, without the DVD in there. If you plot a route before taking it out, it will cache that.

about how much of a radius will it cache? and my car has xm radio built-in would I still have to get the adapter for xm radio

Yes youstill have to buya pioneer xm tuner.

man that sucks