Couple more things...
The E-Pass is becoming the preferred way to go because it's good for use in 18 states. The cost is less for both the transponder and the barcode sticker. The OP said he was in the Orlando area and E-Pass has walk-in locations there. If you go with SunPass, you can get your transponder or barcode sticker in most Walgreens in Florida and call them to setup your account right away.
The cost of gas in Naples and at the Pilot at the corner of US-41 and Krome Ave are much higher than what I've seen further down into Homestead and out on Key Largo so don't let them freak you out like it did me when I went past them.
Florida charges by the axle as most states I've been through. A motorhome and car = 4 axles (unless you've got a tag axle). A tow vehicle and trailer w/2 axles = 4 axles. If you've got 5 axles, you pay the same rate as tractor trailer which is the highest. Not only are the attendants gone from the toll plazas, the toll plazas are gone! All that's left is a framework holding the cameras and transponder sensors. You don't even slowdown for them.
The traffic around the Miami area is crazy. Everyone seems to be in a big hurry to get to the next light before you by switching lanes. The volume of traffic is as heavy and anything you'll ever see. I don't remember it being nearly this bad the last time we were down this way 4 years ago. There's construction everywhere meaning it will only be getting worse.