This game has coop, which means you need to play it with some people you can trust. A level requirement would not help (no levels), as even a naked "level 1" guy would be able to completely destroy your base, steal everything you have and so on. Even wards would not protect you from that.

Some things respawn (enemies, pickables), others do not (mainly ore, trees).

Edit: There are possibilites to protect ones server, but they require you first to host a dedicated server, then you need to add the right mods to it AND you need to be able to configure the mods correctly.

If you - by your own admission - are not very computer savvy, then I would suggest to not try it, unless you see it as a chance to learn something. And be prepared to get utterly wrecked.