Having heard it, I can say having T1 is not necessary since, storywise, T2 does NOT simply pick up where T1 left off. Musically, there are some neat things that occur, the significance of which will be lost if you haven't heard T1. For instance, there is a section of the story in T2 where Neal is talking about just doing his own thing and not really worrying about his spiritual life, and the main riff from Prince of the Power of the Air comes in for a few measures, and then transitions back to the original riff in the song. Although he is much more subtle in the lyrics, the music is very blatantly saying "Satan was clearly in charge of my life at that point in time," but someone who hasn't listened to T1 wouldn't pick up on that. There are some other moments like that as well. But even so, I don't think it's necessary to have heard T1 first. In fact, if he likes what he is hearing on T2, getting that first might be more beneficial because it is more compact. T1 is very long AND very dense, and it took me a VERY long time to even want to absorb everything that is going on. If someone gets T2 first and likes it, they will have more of an incentive to get into T1 and will probably have an easier time with it.