It's not that hard... I did a lot of power washing around our house last year when we were getting ready to sell it, and I had no difficulty learning to gauge the power of the stream so it cleaned without doing harm to our deck and retaining walls.
So if your only reason for not DIY'ing is fear of screwing it up, don't worry. It seemed like a breeze to me.
I need someone capable of reaching second and third stories of the house, reach under the eaves, etc. My understanding is that to effectively do that I would need an extender for power washer, ladders, etc. We own a power washer that was fine for doing one story garage and yard stuff but does not have that kind of reach.
We used this company 2 years ago. We had some nasty algae on the "dark" side of the house. Can't remember what the price was since we had them bring water- we're well out here.http://www.terracleanpowerwashing.com/
We were very happy with their work. We also had them scrub the brick areas around the deck and it looked wonderful. Highly recommend these guys. We have a 2 story colonial and very spot was done.
We used Wilbur (the painting company). They power washed the house and garage and touched up all the paint that peeled off, plus they sanded and repainted the portico so it's really fresh looking. I believe it was in the $1300 range. It was a 2 day job.
mwnewbie