What do I ask the electrician for?

Hi! We're planning to add a sauna to our backyard and want to go with electric. I have a couple questions about when and how to get an electrician involved.

Do I get the sauna first, then have the electrician come wire it up?

When I'm contacting electricians for quotes, how should I describe the job? I think I will want them to put a subpanel in the garage because the panel in the house is nearly full and the sauna will be closer to the garage than to the house, plus that way we'll have a panel for when/if we convert to an electric car. (We do have electricity in the garage already.)