One for the first part, if you do it this way.
Out the airport north exit, left at first light.
Little over a mile is next light where you take two lefts to get on 528 (Beach Line).
Now it gets tricky. When you see signs about paying tolls, get over to the right and go down an "exit ramp" to the toll booths. The toll is 75 cents (perhaps raised to a dollar since I was last there). Back onto the highway and at the end take I-4 west (southwest) and Disney exits will appear soon.
Not sure how to go to Vero Beach but those toll plazas where you have to take an exit ramp to pay cash are found in many places in Florida and other states too.
The EZ-Pass, say from West Virginia or Delaware or other northeastern states, is not honored in Florida. Some rental agents, for a daily fee plus the actual tolls, will set things up electronically so you can stay on the straightaway past the toll plazas without stopping.