I was really fascinated by your question. When I was working on my Master's Degree (Catholic Theology), I did take some history courses. But I studied the Early Church and Medieval Church. That doesn't really help your question :-)
One of the things we learned in grad school was just which sources to trust. We talked about different magazines and journals and different publishing companies. Whenever I pick up a book, I always look at the publishing company to see if I trust it to be one that would be very well researched. I also remember that some were more conservative or orthodox and others more progressive. But everything I know (remember) is really based on Catholic theology.
While I agree that a good place to look be the library. They should have several books to help you look. They should also have access to books at other libraries.
But I think I would start with a local church. I do know that the Presbyterian chuch was "founded" by John Calvin (a French theologian from the early 1500's), so my guess would be that not every Presbyterian minister is going to be familiar with the history of the Scottish Presbyterian Church. But that would still be a good person to talk to. The minister should know some good authors or at least know which publishing companies are the ones to trust. If you do have a Presbyterian church in your area that is of Scottish decent, you might find even more help.
That's where I would start. Call the office one day. Explain what it is you are researching. Ask if you can speak with the minister about some good books or other resources that might aid your research.
Good luck!