As near as I can tell, the Church of Sarenrae has a rather informal heirarchy, with local churches designed around a family, with a Father and Brothers. So similar to a monastic order, really. In that sense, I would imagine given his noble birth and wealthy parents, Gerhardt would likely be the Father of the Church of Sarenrae in Magnimar, though he'll obviously be "taken ill" with some mysterious and lengthy, but non-lethal illness. The Brothers of Sarenrae in Magnimar would be in on the ruse, of course, though anyone outside of the church itself would not likely know that Brother Gars is Father Gerhardt. There is one small problem, though, that I might have to change my backstory for: As near as I can tell, the Church of Sarenrae doesn't seem to have a central authority beyond this Father/Brother system. So I'm going to ask if there's something I missed, and the Church has a central authority for someone like Gerhardt to report findings to.
Sorry about prattling on about what probably seems inconsequential, but I want to get all the wrinkles ironed out.