This is a big job, but it will make the organ sound much better than it has in years. Most people don't notice pitches gradually dropping out from the total ensemble in a spotty manner. But then when all of them are back again, the difference is very noticeable. Older Tonewheel Hammonds have electron tubes in them. The life of a tube will be lengthened if dust is not allowed to collect on it's glass surface.
Dust acts as an insulator, holding the heat inside the tube.
Tube pins and sockets need periodic cleaning, too. Many problems in tube organs are related to oxidized high-voltage pins and sockets, and switch contacts. However, most often a tube has ceased to function. I recommend an annual preventive maintenance plan which includes removing all tubes, then cleaning the glass surfaces, pins, and sockets, and all the switch contacts. Periodic maintenance has been proven to reduce the number of malfunctions in any electronic organ.