If it would be possible to install a democratic goverment then sure. Even though it's extremely unlikely it would improve the lives of the north Koreans. Sadly the way it's been going recently the communist north Koreans have a higher chance of unifying korea under a communist one than a democratic one, although that would most likely result in a long and deadly war for both sides.
North Korea has a very large military, the 5th largest in the world. They have many weapons pointed at Seoul, and going to war would only cause more trouble. Reunification could be costly of both money and lives. Reunification would be great, but it's not practical at the moment. The Korean Peninsula may take a long time to fully re-unify.