If the CCU is completely inoperative, first make sure that you don't have a power supply issue. First check to make sure that neither fuse 33 (7.5 A) or 4 (15 A) have blown. If they are good, then once the CCU unit has been removed check the plug terminals at the back of the CCU to make sure that the CCU is getting power. The test for doing that is described on page 22-38 of the service manual. If the power supply checks out as OK then send it off to NSXe-repair.
A .pdf copy of the 1991 service manual is available in the NSX Prime Library (top red banner). Follow the links to download the manual. Aside from telling you how to do the power check on the CCU it will tell you how to get the CCU out of the console without damaging stuff. You are also going to need the service manual for all the other stuff you are eventually going to have to do on the car since finding qualified mechanics to work on the car is becoming increasingly difficult.
See if you can also score a copy of the 1992 Electrical Trouble Shooting Manual some place as this will also be a valuable asset in the future.
