Testing methods

I would like to know something about testing methods.
Unfortunately my experience is that if somebody wants to change ANYTHING in the hardware or the software (something went wrong or must upgrade for any purpose), the system falls into small pieces and shows strange behaviors: different remained libraries, new error problems, non repeated mistakes. The error repairing became more difficult.

1. So I would like to know: would be again repair system and SAX, some other helper tools? If I have to change a disk (on separate environment) or a video-card, it is a big problem for the system...
2. How you test the system (I see only same tests on same architecture), repeated install/uninstall, update/upgrade/downgrade and regression tests? The system stability (against the changes) now very slow... dynamic test are missing, I think.
3. Could you improve the program and system error messages and error seeking ("it is an error", unconfined error", lots of error with same error messages - "CHANGE HAT")?
4. Could you make simplier and wider (not for the files/directories but the programs/programgroups) useful apparmor program (not for the gurus, but the lamas)?

Thanks in advance
venember