There is really not much to do for summerization if the winterization was done properly, so you may want to contact the dealer to be sure of what was done. What I would do:
1. check fluid levels (oil and coolant) and make sure the oil is clean and was changed during winterization
2. fill the tank up with fresh gas
3. charge the battery then hook it up to the boat (should have been disconnected for winterization) DO NOT CHARGE BATTERY WHILE CONNECTED TO THE BOAT
4. do an overall check of things, make sure everything electrical is working, and all levers, linkages, etc. are free and working
5. clean and wax boat as needed
6. do a test start hooked up to the hose for a minute or two to ensure it runs well (make sure you know what you are doing or you could flood the engine)
7. drop it in the water and have fun!
One last thing I would do after the first or second run is to replace the spark plugs since the fogging oil, added during the winterization process, can foul them a bit. That's it, hope this helps!