I have never heard of a product called nextgen so the answer is no there is no importer. We have importers for the competitive gallery products. We do not make importers for the thousands of plugins or mods made for various forums. I do see doing a net search that gallery product appears to be some wordpress plugin.
You could inquire about costs of making sure an importer for you through the contact us link. Our fees are 70.00 an hour for custom work which is about half the industry standard.