Your query relates to the motorhome function of your vehicle. In this context the converters name and model would be more usefull than that of the base vehicle.
To answer your first query, the selector switch "up and down" will probably select either main (starter) battery, or auxilliary (habitation) battery, to supply the habitation electrics. I would advise only selecting "main" in an emergency, since if this does relate to the starter battery, you could discharge that battery and be unable to start. If you have anything resembling a manual, please do check in that. (I prefer the use of the term habitation battery rather than leisure battery, which refers to a type of battery.)
As regards you second question, I am afraid that your description is insufficient. If you could manage a photo, that may help. You may do better consulting a motorhome specific forum such as "outandaboutlive", but please do supply motorhome details.
