Got a question about Dark Heresy and gameplay.

I am interested in joining a game as a techpriest, but I'm wondering about how they play, specifically in terms of gameplay and tactical situations, but also in roleplay and fluff-based terms if you've got time left over. I've tended to focus on the Imperium and 40k in general from the standpoint of the guard, so this is not something I'm particularly used to, or that I'm knowledgable about. I know a bit about the mechanicus in a general sense, but not much more 'cept a few small tidbits like that there are some techpriests who work in the fields of genetics and biology, etc.