The Formaldehyde should be completely disapated by now. But if it concerns you Home Depot used to have home test kits for it from "Healthy Home".
Or get a DIY home Formaldehyde/Explosive Gas test kit...

The Recreational Vehicle Industry Association says...
"Ventilate. Open a unit’s windows to allow fresh air in and run any fans and the air conditioner to lower the temperature and humidity before each trip. If a unit has a pungent odor or you experience any irritation, the best bet is to ventilate the unit."