I would do that deal myself.
After five years I had to change out a Honeywell valve where the gears disintegrated. $40
That solar one also has a mixing valve on the spigot side. It mixes hot and cold to output what I set at about 120. I can let the tank in the summer get up to 160 degrees, and be safe not to scald anyone. That also makes the 80 gallon after mixing, act like 160 or 200 gallons of hot water !!
That price also included a 1/20 hp little pump to circulate the rooftop path.