We're not talking about a disposable, your HVAC system has a significantly large price tag. As you contend, doing is learning and self-sufficiency is a virtue,

We're not talking about a disposable, your HVAC system has a significantly large price tag. As you contend, doing is learning and self-sufficiency is a virtue, I agree with the sentiment wholeheartedly and practice on systems whose complexity I understand(and/or I've broken and learned through cost & attrition). The potential I speak of is costs; blower motors, controller boards, micro controllers and transformers can be replaced when your common shorts another wire or the previous installer/service guy decided not to wire according to specs due to broken wire(s), retrofit anomolies, myriad of other reasons. Of course, we learn by doing, choose your lessons accordingly.