Like most things I do, I have no clue what I am doing until its done.

Before this, I have never seen a vent up close let alone installed one.
But why should that stop me??

I got lucky and picked one up off Kijiji.  ( actually got it for $5 )

It was a little mucked up.
Had to do some cleaning, but it fine.
The flange was not perfectly straight, but neither was the roof.  I did the best I could.