Guidance

Dear Group,
I'd like to ask your experienced guidance in the research of my Arrambide branch that has apparently hit a brick wall. 
Martin Arrambide died 11/16/1762 in Salinas Victoria, NL and his burial entry states he was Europeo.  In my experience with family members that were born in Spain, the entries state he was from los Reinos de Espana/Castilla, or something to that effect.  This led me to research the surname Arrambide a bit.  It's probably Basque and possibly from France.
In Israel Cavazos Garza's, Breve historia de Nuevo Leon, he is briefly mentioned as such:  Ya en 1741, el obispo de Guadalajara, don Juan Gomez de Parada, establecio una escuela formal y nombro como maestro a Martin de Arrambide, encargandole mucho la buena educacion de los ninos. 
Does anyone know where to research this type of order or mandate made by the bishop of Guadalajara of that time?  Would this be found in some place other than Diocesis de Guadalajara?  Discovering this would probably yield more information on Martin's origins and possibly his age, either of which would be a great place from which to continue. 
Thank you so much for all your help.     Alice Blake