NO! There is a much easier way - rather than deleting everything.
Connect the BB to your laptop or PC and start Desktop Manager.
Go into the Backup/Restore function.
Click on Advanced - on the right hand side you should see the Device databases.
Click on the Address Book and select "Clear".
That will wipe out the Addresses and leave the rest of customer data there.
I used that method just today to clear my calendar on my BB, straighten out some goofed recurring events in Outlook and then sync from Outlook back to the BB.