Another note of caution. The unit like to run hot. In that the gimbal assembly requires a lot of heat to keep the gyros happy. The front of the unit will be quite hot to touch, whereas the rear of the unit where all the computer cards are likes to be at a cooler temp. When installed in an aircraft there is a constant movement of air thru the rear of the unit. If you get it up and running I would place a fan at the back of the unit to force air thru the rear which will then escape thru the underside of the unit.
The front side covers of the INU can be removed if there if a lot of fluff stuck in the heat exchanges. This fluff can be removed by a strong brush, just make sure the top lid if firmly in place so that nothing gets into the gimbal area. These older mechanical systems are a little finicky. :-)