The drive is not terribly complicated. The most difficult part is going from the Port Everglades port to the Turnpike or I-95 since part of that is on city streets and we've found the signage could be more helpful. Our experience is that you don't realize you need to be in a certain lane until you're almost right on top of the turn. But that's actually a pretty minor complaint.
Once on the Turnpike (our preference, we live very close to WDW) it's a pretty boring drive of about 3 hours. There are a fair number of rest areas along the way.
All the major car rental companies have offices on Disney property. Everybody mentions
Alamo at the Car Care Center, but that's not the only option. The other major companies will have offices in the hotels along Hotel Plaza Blvd. You can drop the car there and then walk to Disney Springs to catch a bus to your resort.
You'll be at WDW much earlier than 4 pm assuming a normal debarkation process. More like noon to 1 pm.