So do I need to call Sprint before making vacation plans to verify coverage so I wont have outrageous charges for using the phone and apps while on vacation?
For data -
Menu > Settings > Wireless and Networks > Mobile Networks > Data Roaming
If that's off, the phone will not connect to data while roaming.
For voice and text roaming, there should be information posted to their web site about the cost. You could also call as you said, I'm sure the CS reps will know.