Yes the compartment doors likly the standard CH key.
IF you had the number written down for the FIC (Fastec Industrial Corp.) main door key it can be ordered..should be 3 numbers stamped on key. I think the numbers are also stamped inside the lock if you or once get access. Replacement keys are available but need the number. I keep our spares in truck. I have the number written down-in the campers manual- which is in the camper...
On ours the rear compartment door which opens to dinette seat box is large enough for a child to enter. Either lifting up the seat box top, have to finangle the cushions- or possibly thru inside cab door, to open the main door from inside.
I havnt a clue what lock smith would cost-Id call around. Given options might be cheaper before tearing stuff up. Outside cab you can buy key- main door breaking door window would offer opportunity to change it out to clear. Wouldn't think cheaper-
Edit- as LOWELL731 mentioned there is a master key for the FIC locks- taking camper to dealer in your area they could open for you. And sell new keys.
FIC keys