Q:

How do I remove this old bathroom exhaust fan?

My ancient 1960s bathroom fan (a NuTone 8832) stopped working. I removed the cover and fan, but the "metal box" assembly is still in the ceiling. I'm not sure how to get it out.
Here's the unit, with the cover and fan removed:

What I've tried:

undo all exposed screws. didn't help.
look for a way to tilt or pry a piece of it down. no luck there either.

Any ideas how to get this box out of my ceiling? I bought a new fan unit, but I need to get the old one out before I can install the new one! :)

A:

I am assuming that new fan is bigger or same size.  

You have joists that this is nailed/screwed into.  Try not to damage adjacent drywall.  I am going to guess from this picture your joists are on the top/bottom of picture.
This is because your exhaust/and electric look to be coming from the left.  I would cut straight along the top and bottom (using picture) of the fan cut-out and extend that about 2 feet to the left. 
Remove drywall
Take out old fan with hammer or screwdriver or just club it out gently.
Install new fan - with the 2 feet you have room for maneuver duct into fan slot and electric work.  
Put new piece of drywall on and then you have 3 pretty easy seams to mud/tape.

