Your 14 week plan will have only 7 weeks of Dianabol usage, and spread out over time, so personally I'd be confident in just running it and then, for the sake of knowledge, taking a single test at the end point.
As you probably know, high AST and ALT would not necessarily signify anything, as they can be increased from exercise (AST moreso than ALT.)
In contrast, elevated GGT (or GGTP) will be from damaged liver cells and is a reliable indicator of liver damage if health otherwise is fine and provided that there's no excessive alcohol use, or use of NSAID's, aspirin, or acetaminophen, or some other drug use.
Moderate elevation over the normal range is okay, but twice the reference limit says things have been pushed. (Simply getting rid of the cause will be all that's needed, if that's the case.)
You may have to ask to have GGT included.
Also look at serum bilirubin.
Another key marker is serum bilirubin. This preferably will not exceed the reference range, though there are a few people who are, for them, normally above the reference range. But most likely, if above normal, this would be cholestasis or a bit of it. Certainly if twice the top of the reference range, I'd consider that too high and next time do different personally. I expect this is unlikely with your protocol though!