Tom, I don't know what your mystery is or how far advanced your family history might be, but have you tried logging onto Scotlandspeople at
http://www.scotlandspeople.gov.uk/ ?
This is a very valuable source of information, particularly in the Old Parish Records. For 6 pounds or equivalent, you get a week's unlimited searching of Scottish records and can order copies or certificates on line.
Another source I found most helpful was the "Statistical Accounts of Scotland".... I forget the URL but you will get it on Google.... these are two sets of descriptions of the parishes in the late 18th and early 19th centuries and so give a wealth of local information. Most were written by clergy who were, of course, usually the best educated and best-informed folks in the district. You need to know the parish from which your ancestor came.
I am not suggesting you abandon your trip to Scotland, but you might be able to get the same information from the comfort of our own computer room as you can in a library in Scotland, and not have to wait 18 months to get it!