There is a world of difference between organ repair and piano repair/tuning.
It requires a thorough knowledge of electronics and some pretty expensive specialized equipment.
Unlike pianos, where there are a number of similarities between instruments, organs vary greatly from brand to brand and model to model.
This requires keeping schematics for each brand/model. Obtaining parts is another story.
It is often difficult to locate electronic parts for older instruments.
In general, organs should not need to be "tuned".
For the last 30 years or so they have used locked oscillators and/or digital tone generators. Only the really old instruments used a tuneable can type oscillator.
Instead, the usual cause of them sounding out of tune is dirty contacts (in older models this was a wire that touched a "bus bar" when the key was depressed).
Pipe organs are another story all together.
They require a different set of skills and usually require two people (one at the console, one up in the pipes).