I can't imagine the factory charged the system before installing the dash .
So yes it can be recharged .
Replacing the evaporator , while that's a different story .
What chassis is your coach built on ?
Any idea of the dash HVAC system supplier ? Evans ? Denso ?
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.