I need to replace the cylinder lock I bought for my Nissan altima GXE 1997 but it seems too difficult to do. I don't have the diagramas or schematics and the piece does not have intallation instructions. I'm doing this because my wife lost the ignition key and the locksmith charges over a 100 bucks when I just bought this piece for 40...

Haynes repair manual #72015 that can be found at many auto parts stores for around
$ 16 has the info your looking for on page 12-6. Be sure to remove both positive and
Negative battery cables then wait at least 10 minutes before working around the steering
Column. This will ensure there is not a chance the airbags could possibly accidentally deploy.

Procedure should be similar to the following:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-honda-civics-46563-2.html#post224842