From November, 20 2017 restart is not required for Class Changes, so they will be done in a following way:
After Ticket with Class request will be created, you should expect an answer from Support staff, where they will report the transfer of your request to the specialist.
From the moment of the answer, Class change will be made withing 12 hours. So please, don't plan to participate in any important events. For the Class change process your character will be blocked. You will be informed about character's availability in the Ticket.
Class changes will not be made on Sundays!