I thought Snoddie was the local Public Health Doctor, which was why he came to so many disagreements with Cameron over the best policy for dealing with infectious disease outbreaks and the like? He probably also had a role in investigating local unexpected deaths (without actually being a pathologist), hence someone's idea that he might have been the undertaker: he certainly looked like one!
I'm also pretty sure that the house used for the Dr's house/surgery was in Callendar, and agree with Megan, there's still an "Arden House" there that looks remarkably like the one used ofr the show set. (And yes, it's in Perthshire)