Forest River and other manufacturers, are infamous for only providing generic owners manuals that aren't worth the paper that they're printed on.
FR has no download site nor any other than the generic one here.
you'd do better looking for a Coleman manual and see if any of it is useful. i believe Coleman is one of the few to provide model-specific manuals.
you can go to specific items' manufacturers' websites, like Dometic, Suburban and so on, for their manuals.