You could wash your car, I would recommend doing it yourself and not injecting any water into the fender liner right under the filter, that's how you get water in the filter. As long as you're careful about it, you shouldn't have a problem.

The resonator (at least for me) was a big white box beneath the splash gaurd in front of the passenger wheel well. You'll definitely see it once you take off the 8 or so screw/pop things that hold the guard in.