You're going to have a ball, don't worry. If you have trouble inputting waypoints, just use the GPS as a map, buy the chip for the Florida Keys, for some brands it's one chip, for others there is one chip that goes from Palm Beach to Marathon and another chip that goes from Marathon to the Dry Tortugas.
If you find yourself in doubt during the trip, call me on my cell at 954-980-2643. The Keys have been my boating back yard for almost 50 years now. It's a pleasure, as Medicine Man has said, to share their beauty with our Friends.
As you travel down there, make notes of the landmarks, buoys, etc. so on the return trip you'll have some known reference points. Watch your chart so you know what key or island you're parallel to. If you're completely lost in terms of course direction, but have a land reference, use the compass rose on the chart to plot your next heading.
Just remember that the further south you go in the Keys the more your heading will take a westerly course (On the southbound leg) thus the 245 to 255 degree compass heading as a general direction from about Islamorada south on the ICW side.
You'll do fine!!!