the 2nd generation theory is out of date. if you haven't had diabetes or you aren't borderline then i wouldn't worry too much about it. i'm assuming that your grandfather took insulin correct? but just to be safe you should get a blood test to make sure that you're ok. What GH does is decrease insulin sensitivity and therefore can be similar to type 2 diabetes. Whether or not the effects are permanent are yet to be known but there are a lot of bros around that have been on GH 10 years plus and haven't had any problems.
taking insulin with the GH might actually make things worse for you. the reason why you take insulin w/ the GH is to combat that densensitizing effect however i think that by doing that it further inhibits your endogenous function and production of insulin.
i would wait and see a little more about what some experienced guys have to say about it.