Malamute
As far as the NPS being a scary evil entity by having M-16's and backing up the military if needed, I hope that comment was tongue in cheek, because I had to laugh when I read it.
It'd be tounge in cheek if it wasn't, unfortunately, true. There's a great bit of variety, but especially in the border parks, rangers are becoming less and less the friendly folks that help with a flat tire, and more the kind that:
Set up remote cameras to monitor potential "smuggling"
Use night vision to observe visitor activities in campgrounds and popular areas at night.
Conduct "operations" with other federal agencies.
True, and in my opinion, sad.
You're correct that a good number of the seasonal folks don't know which end of the gun is the business end...but the full-time folks have at the minimum a side-arm, shotgun, and AR-15.
As far as gun laws go... the parks are all different, although for the most part, ithey're a "no loaded firearms" area. This varies as some units allow hunting in season, but you've got to check on a case by case basis.
For what it's worth, NPS units also set their own rules about fishing and hunting, regardless of state regs.