Yes, the interstate interchanges are very well marked. Using your GPS is good, as is a map if you know how to read one. We always get a Trip Tik from CAA as a backup to the GPS. This has the advantage of noting interchanges with very close gas, food and lodging.
Note that the times given on sites like Google Maps or CAA are driving time estimates only. Actual TRAVEL time is usually more, adding for things like border crossings, and stops for gas, food, or bathroom breaks. Not to mention your own average speed on the road.
If you were to leave around 4 am and stop at 7:00, I think you'd be somewhere between Charlotte NC and Columbia SC. There are plenty of chain hotels/motels just off the interstate in both places. But you would still have quite a long drive (7-8 hours) the next day. If you only want a 6 hour drive the next day you would have to get closer to Savannah on your first day.[/QUOT
Always get the trip tik, just a fun thing from childhood with GPS backup. We leave from Durham Region around 3 am and stop in Hardeeville SC for the night