Ken,
Well Sir, we too have the C-7 330 HP CAT. At present, we have no leaks (knocking on my head). But, your plan would be just like I'd do. And that is, if you have to, change oil and remove the filter and see/investigate with a good flash light and whatever else is needed to really get up and close to the are you think the leak is emminating from. If nothing else, I'd maybe get a can or two of spray carb cleaner and douse the area real good and then, do what you can to keep an eye on that particular area. See if it starts up again. Let us know what you find out so that we "brother" C-7 pilots can keep an eye out too.
Scott