If you're just going to be there on vacation I would grab an oil pan heater. There are lots of different models, like replacement dipsticks, etc. but the ones I've seen are magnetic strips that stick to the outside of the oil pan and keep your oil warm. Just zip tie the cord to a few places to keep it from dragging or getting caught in something moving and you're golden. If I was going to be in Minot ND for a few weeks in the winter, this is what I would do! Even though sometimes it get real cold in new england, you really don't need a block heater even when it's like -20 in the AM.
Freeze plugs are usually copper (but also other metals...copper is expensive) plugs with a real tight press fit that you hammer into holes machined into the block. They're there in case someone uses straight water instead of water/antifreeze and leave the vehicle in very cold weather. Ideally, instead of the ice cracking the whole block, the ice would push these plugs out and save your engine block.
To install a block heater you would drain coolant and then try to punch one of the freeze plugs out. One way is to drill a hole in the center, screw in an attachment for a slide hammer to that hole and then pop it out that way. You can also just bang it in with a chisel and then pull it out once you've got it loose. Then the freeze plug goes right into that hole and seals it up, and there is a wire coming off of it, zip tie that to various non-moving parts so that the cord doesn't get caught on anything, fill the coolant back up and you're good to go.
this photo isn't a KJ 3.7, but on the block the gold colored things, those are freeze plugs.
