I know that Church. It is right about two/three blocks from Ground Zero right on Chruch street. Can't remember the name of it, but it has the iron cross on display that they found in the rubble after 9/11.
Yes the E train will take you to 42nd street, look for the exits that say 7th Avenue.
If you have 8 hours that is more then enough time. I hope you enjoy your trip.
Mary Anne