The antenna can simply be unscrewed using your hand, and the wheel skirts can be removed by unscrewing two screws with a flat-head screw driver.
I too was curious about removing the skirts before washing the car, but i decided that it probably wouldn't cause any damage if i left them on. I went through an automatic "brush" car wash with the skirts in place and there was no harm done. The only downside though is that the rear wheels dont get very clean... Do so at your own risk, but i think you'll be okay.
Gasp! Ok first I would highly suggest not using a car wash. The best of car washes are only going to be maybe 3 out of 5 stars. You either have brushes that will undoubtedly have contamination in them (ie the mud from the big truck that just went off roading after a rain storm that went through the same car wash right before you), or touchless which is a bit better is going to have to use harsh chemicals in order to break the dirt down.
So if I haven't talked you out of it, your probably better off removing the skirts. Even if there's no brush they probably spray some wheel cleaner on the wheels, and this isn't something you'd probably want getting on paint. There's actually a tool in the jack kit to remove the skirts, but it's probably easier just to have an extra stubbie screw driver in the glove box or in the rear storage well.
Bend over onto one knee in front of the skirt. Look straight at the skirt, you will see to things that look like screws (Large) Use a quarter from your pocket and turn the scews counter clockwise. (1/4 to 1/2 turn.) Pull down on the skirt and it is removed.
They are harder to put back on in reverse sequence.
Here is another thing to remember about using brush car washes. The bottom black trim on our Insight is nothing more than tape. Brushes will peel back the leading edge of that tape, including any other OEM decals on the car over continued washings.
FWIW, I generally pull the spats off and use a coin-op hand wash first to flush out the wheel wells and get the crud out from under the rockers, underscuttle panels front & rear, etc. Then I put the spats back on and run it through an automated, brushless high-pressure wash we have nearby. Never had an issue with the spats going through the auto wash system. (People do get a kick out of watch ing us take the silly things off & on..they're a PITA, but also, too cool!)