Follow EPA's recommendations for cleaning. Soap and water, wipe dry. Do not cut plastic in the ducts. Mold spores are everywhere and any continually moist surface will grow mold in the dust that collects. Monitor the indoor %RH. What region do you live in? <50%RH is nice in a home.
Do not get hyper start cutting. Keep us posted.
Regards TB
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"