Does the bumper have to
be removed first?

 

Yes the bumper has to be removed to take the diffuser off of it.

 

Yes, according to other users, the rear bumper must be removed. There is no work around but removal is pretty straight forward.
Youtube has instructionals.

Did you get the new stock diffuser or aftermarket?

 

I bottomed out the rear going up a steep driveway (didn't even know that's possible) and scratched the one side of the diffuser!

 

Is removing the bumper pretty painless? If I use the protective tape along the top edge of the bumper will it be enough to not scratch anything?

 

Honestly yeah removing the bumper was the first thing I did on this car (on any car for that matter) using a youtube tutorial. So you can definitely do it

Another helpful tip I got was to place something on the ground behind the car, so that when you lower the bumper to the ground you don't hit concrete/pavement/whatever surface you're working on. I used a old blanket

 

Thanks man. I appreciate it!