What breed of dog can be a service dog?
Many breeds make good service dogs. It depends on what skills the dog will need to perform and what size dog you are comfortalbe with. There is no one breed that is best.

Can my dog be trained to be a service dog?
Any dog being considered for service work must be evaluated prior for temperament, socialization skills, ability to learn specific skills etc. Since working dogs are in the public they need to be appropriate candidates for working partners. It is a tall order for a dog that isn't inclined to enjoy such a public life.

How long does it take to train a working dog?
Dog teams are all unique and the time varies depending on the time spent training. Typically it can take a year or more to get a dog trained to certification level.

Will I have to use a clicker and treats for the rest of my dogs life?
No. The clicker is used as a marker to teach some new behaviors and is faded when the behavior is reliable, as is the food reward.

Do I have to use food as a reward?
No. It is simply a fast and effective motivator. There are other options for rewards.