The attire is semi formal. Nicer cocktail dresses, midi dresses, suits, and slacks with a sport coat and a button up are appropriate attire for this event.
No, there will not be transportation provided for guests. The hotel block is very close to the reception venue. If you plan on drinking, please plan on using a rideshare or carpool service to safely go to and from the wedding and your residence/hotel.
There is parking at the church, however, there is only street parking available at the reception space. Because it will be taking place on a Sunday, you will not have to budget for paying for street parking. There is a decent amount of street parking close to the reception space, so walking shouldn't be a problem. If it does fill up, parking at the Savannah Civic Center will also be free and available to the public.