When I search for a MAF (mass air flow) sensor on a parts website, I see some that are sold with the housing and some without. A mechanic gave me a quote that correlates price-wise with the full sensor + housing part. Is there any reason why I'd want to replace the housing (and not just the sensor) if the old one is not broken/cracked?
I wouldn't if there are no obvious defects in the housing. Sometimes parts stores will only sell items as the complete package. When buying a thermostat from oreilly's auto parts for my forenza the only thing they would sell me is the whole housing unit with the thermostat. When searching on ebay, I found the thermostat without needing to buy the housing as well. Moral of the story, always look for the single part you need before buying the entire unit. I'd save yourself a few bucks and just go with the sensor itself.