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Yes, regular car fine. You will probably have to hike to see the lava flow up close. If you want to do this, bring sturdy shoes, good flashlights and plenty of water. The lava can be very sharp if you fall. Every day conditions are different so check with the (excellent) ranger center for latest updates. The Rangers give interesting scheduled talks and walks and there are great exhibits at their HQ and at the Jagger Museum on the brim of Halema'uma'u caldera The Park HQ and Ranger center are located not far past the main park entry gate. There's also a good art Gallery just past the center and the historic Volcano House inn & restaurant. The village of Volcano, outside the Park has a few galleries and restaurants and many cozy little houses to rent via vrbo, Airbnb, etc. Because of the frequent mist and rain, the Volcano area is lush and dense with tropical plants and flowers. It's also cooler than either Hilo or Kona.

You do not need to be part of tour granted you have your own transportation. We just grabbed a map from the Park Visitor Center. Enjoy but make sure you have a good windbreaker. The wind, even when warm, can really kick up and chill you to the bones. We have seen many people unprepared for that. Once you get away from the main areas, traffic lightens up and there are many trails worth exploring. Start your day early.