While the others have given you some good information on physician clearance and programming, I just wanted add a quick note about rapport with the client. Your client has obviously gone through a major procedure, which affects a person both physically and mentally. It will be important to establish a good connection with the client and build a level of trust (as with any client). As trainers, it is important for us to meet the client where they are with regard to their willingness and ability to change.
I would make sure to encourage and support this client for the small steps, and understand that a lot of preparation (psychologically) went into their decision. Best wishes to you on working with this client, it sounds like it could be very rewarding.