The driver's side was super easy; no need to remove the light assembly. Things are a little tighter on the passenger side (there's a ground wire that gets in the way), so I removed the light assembly; it took a few minutes longer, but again very easy. I think I was done with both sides in about 10 minutes.
It looks like it can be done with both housings in the car, but I just could not get the H11 oriented properly while reaching into the housing with it still in the car for some reason.