Dehyration/Drying Question

If you used the curing packets I wouldn't worry. It packs quite the punch of salt and nitrates for preserving.

We have had great luck and results over the years with the following strategy:

We always cook poultry, pork, and ground beef. We soak raw meat for jerky in salty or sweet stuff, then dry, no cooking.
Cured ham also works, although it can be salty if you eat it plain. We also dehydrate cured or pre-cooked sausage (usually as thin slices).

I suppose one can skip cooking ground beef, but the tremendous surface area so easily breeds bacteria (e.g. E.coli), etc. that I'm not sure this is wise.

if you are using something like thinly sliced flank steak for your jerky there is no need to pre-cook it but if you are using poultry or ground meats you should make sure that you cook the meat first.

I went and looked up the jerky making info on Nesco's site and yes, they have you using raw ground beef for the jerky. The seasoning packets they sell are the key to it though. If you can I would get your hamburger ground for you in person – if you have a grocery store that still does it (Safeway here does for instance).
http://www.nesco.com/customer_support/owners_manual_download/?lang=english