I currently run a DC system with EZ track. I have several turnouts and two crossovers on my layout. If I switch to Bachmann's DCC system do I need to change my track and switches?
Your existing track, turnouts, and crossovers should work just fine on DCC, but your locomotives will need to be converted to DCC if they don't already have dual-mode decoders installed.
You can use your current DC controller to power the turnout's and crossover's solenoids since DCC controllers don't support them. Unless you want to replace them with Bachmann's DCC versions that are powered by the rails.
If your layout has any loops that allow a train to change direction on the mainline, you'll need a Reverse Loop Module to change the loop's polarity when it detects a short.
An aside: Are you planning to get the E-Z Command System or Dynamis Infrared System?