I can't say about NASA, but I can say about my experience at ESA (European Space Agency), where I worked on Mars lander hardware. You have very very formal procedures and detailed checks as soon as you approach any parts which is going to fly.
The simplest task you can imagine takes incredible proportions (for good reasons).
Disconnect and reconnect that plug? Please inform persons X and Y, person Z must be present, only person W can touch that plug, and do perform a functional test according to the procedure in this document before and after and file these reports etc ...
Cleaning a part? Oh glob. Get ready for 3 months of adventure talking to planetary protection experts and book the cleanest room in the continent.