I meant to respond to this when I first spotted it, but I was having a busy night at work…
In addition to the other good advice you’ve already received:
If you like cemeteries, check out Colonial Park cemetery in downtown Savannah (in addition to the ridiculously picturesque Bonaventure.) Add it to a little walking tour - see the squares, pop into Leopold’s for ice cream, walk through the cemetery, grab a slice of pizza at Vinnie Van Go Go’s in City Market, walk through the zillions of art galleries. Instead of Paula Deen’s, I’d recommend lunch at Mrs. Wilkes’ Boarding House one weekday. For the best view around, take the water taxi across the river for dinner at the AquaStar at the Westin. Ask your front desk clerk or hotel concierge for directions to Desposito’s in Thunderbolt - total dive of a seafood shack, with the freshest seafood in town.) If you aren’t nauseous, take one of the riverboat cruises - they’re great fun, especially the gospel brunches. Also, if you are an art afficionado (sp?) check out the Telfair Museum and the adjacent Jepson Center. There are lots of house tours (besides the very lovely Mercer House) that are worth your time: the Andrew Low house, the Juliet Gordon Low (founder of the Girl Scouts) house, the Green-Meldrim House (Sherman’s headquarters when he captured the city,) the Davenport House (the first of the homes restored during Savannah’s revival,) and so forth.
If you like museums, the Railroad Roundhouse is pretty interesting (adjacent to downtown - easy to walk to if you aren’t driving,) the local history museum next door at the visitor’s center, the Ralph Mark Gilbert Civil Rights museum (across the street from the Roundhouse and the Savannah History Museum,) and the Ships of the Sea Museum (in a house worth the tour, even if you aren’t so into ships.) All of these are on the western border of the historic district. If you have a car with you, I highly recommend the Mighty Eighth Air Force Museum in Pooler (about 10 miles west of downtown, just off Interstate 95 at Exit 102.) (And don’t forget to budget for parking with your hotel, if you’re staying downtown.) The various trolley tours are great fun, and offer a good overview of the historic district, and there are other more specialized tours - Ghost Tours, Movie Tours, whatever.
Other nice things to see: Trustee’s Garden (eastern edge of downtown,) Old Fort Jackson (War of 1812 fortification, fun place to watch the dolphins and pelicans,) Fort Pulaski (built pre-Civil War - one of Robert E. Lee’s first assignments out of West Point - you’ll pass it on the way to Tybee Island.) If you have a free day, I’d also recommend a quick trip to Jekyll Island’s Millionaire’s Village and/or St. Simons Island - both a bit more than an hour south of Savannah.
On Tybee, you’ll of course stroll the beaches and maybe (if you’re up for it) tour the lighthouse. Eat spicy food at the North Beach Grill, grab breakfast at the Breakfast Club, enjoy the general laid-back tackiness that IS Tybee, and sleep late.