I didn't install the TEMPest fans, but I did install two 60mm fans in my C11. It's not really that hard to do, but it takes time.
Disassembly of a Celestron SCT isn't all that difficult. The biggest problem is if this is the first time the scope has been disassembled, the tube is hard to separate from the rear casting. I had to use a wood block and a hammer to tap the pieces apart when I disassembled my scope. The steps are:
- Remove the corrector plate and secondary mirror assembly. Be sure to mark the orientation of the corrector plate, there's only one right way to put it back. They are typically marked at the 3:00 position (when looking at the front of the scope) by Celestron at the factory, but don't take a chance, make your own mark.
- Remove the focuser knob and then the bearings from the back of the scope.
- Reach into the OTA and remove the snap ring that acts as a safety stop to prevent the primary mirror from sliding off the end of the baffle tube.
- Screw the focuser shaft until the primary mirror disengages from the shaft. You can now slide the primary mirror assembly off the baffle tube and out of the OTA.
- Put all your glass parts in a safe, protected place while you play with the metal bits.
There are threads out there (Astromart, the C14 Yahoo group, and here I'm sure) about disassembling SCTs. You can get more details and more cautions there. As I said, it's pretty simple, but there are things to watch out for (sticking corrector plates, corrector plate orientation, grease on the baffle tube, out gassing, etc.). There are also other things you can do while you have the scope apart (cleaning and regreasing the baffle tube, cleaning the primary, secondary and corrector, flocking, etc.).
The rear casting is aluminum and can be worked using wood tools. Really. I used regular drill bits and a hole saw to make the cuts required in my rear cell. Once the fans, switches and wiring were installed, I cleaned out any debris and reassembled the scope. A few minutes' collimation and I was back in business. Of all the modifications I made to my C11, the fans were tied with the internal dew heater for the best and most effective.