Anyone out there had experience removing the vent pipe running out of the ceiling? Starting a remodel of our 1978 and the bathroom ceiling has to be replaced. The pipe nut turns, but the entire pipe turns with it. I tried getting a pipe wrench on it, but no luck. Also, the vent pipe has no cover on the outside. Is it supposed to have one?

Sounds like you need a total replacement
Get a new vent pipe termination jack with a top see if you can find a metal one it hold up better
I would cut it out completely use a hacksaw blade cut from the inside of the pipe to the outside best to install all new parts so you won't have future problems