It's recommended to rent a car for your trip to Maui to have the freedom to explore the island. Some locations may have limited parking, so plan accordingly. Gas prices are around $4/gallon. Traffic can also add extra time to your trip, especially on the Road to Hana. Consider taking a break from driving and using a shuttle or tour service for some excursions.
If you have less time, consider skipping the Road to Hana and Lahaina, sticking to central Maui instead. If you have more time, consider taking a day trip to the island of Lanai or taking a helicopter tour of the island. Don't forget to bring sunscreen and bug spray for outdoor activities, and make sure to make reservations for popular restaurants in advance.