You can do the action, intonation and change strings with confidence of not doing any harm, I believe.
You may find that you adjust it to where you dont want it to be, or it gets a while to get used to some idiosyncracies, but you shouldnt do your guitar any harm. Its just use of a screwdriver and/or allen keys.
The truss rod is nothing to be terribly afraid of, but the scare stories arent wholly unfounded - you can permanently deform the neck in an undesirable way or unscrew the rod (I've done that one before, back when I was taking the first steps of teching about 10 years ago, very shortly after I got my first guitar)
theres a caveat to these things, a floyd rose shaped caveat. If you have one, there are some extra pointers you'll need to not lose parts of it. send it flying, or just pull your hair out. They get really easy when you know what youre doing, but they can be a pain before then.
However, how you actually do all these things varies from guitar to guitar, so what guitars?