I dont know what CW actually does for their $300 service, but if they do it correctly it is worth $300.
I rotated these pics from every position on my pc, they still posted sideways?
The recommended cleaner and the recommended treatment. This is not including the roof paint sealer if your unit needs it. There are some really good paints available now if your roof needs it. Some claim they help AC unit 10-20%? As stated the Dicor self leveling caulk is some awesome stuff to seal around vents, edges, and etc.. any possible leak or existing leak.
Some use spic and span, plain water hose psi, some use pressure washer, whatever just use a brush and some cleaner if nothing but some Dawn dish soap.
I have neglected mine for few years so it is going to get a really good cleaning and sealing.