What exactly do you mean by "culture shock." Are you going to a spiritual center to do this?

I also don't know why the room would be dark. In the decades I have meditated in myriad group settings a dark room was never a thing. Frankly, a dark room would put me off. Of course I have gone to candlelit contemplative services, but I think that is a different thing.

Finally, if you have meditated before, and you don't seem to feel comfortable with the "culture shock and stuff" of this venue, why are you forcing yourself to participate? It sounds stressful.