Cleaning A/C coils: DIY or hire a pro? (See March 8 update)

Do yourself. Just spraying water on it will do the majority of cleaning. It all should be waterproof.
Of course, you take the white cover off to do this.

The pro AC guys have use a cleaner they spray on the coils, let sit, then spray off, it gets it clean with little need for a brush. Also, spray from the inside out if you can to blow the dirt out, not in.

Clear any debris or bugs out.

That's about it.