what is the cost of equipping my garage for electrical charging for a tesla series 3?
Ask an electrician. Costs will vary depending on a lot of factors and how fast of a charger you want.
Yes, you need a qualified electrician to come out and evaluate your house. Get more than one quote. You can upgrade to 120V or 240V , which is quicker charging, You might have to upgrade the whole house electrical service or just add a new circuit and plug in the garage depending on your service.