Are these normal types of repairs expected for a 40+ year old home? Can they be done with taping and mud? Or do I need to look for structural problems?

I'm a newbie to home repairs and can only afford my own hourly labor :-)! Is this something a novice could handle?

Thanks for your input!

Plaster or dry wall?

Straight cracks or irregular?

Textured surface or not?

The inside corner is straight up and down in the corner, though attaching to the horizontal crack now, hard to see in the pics, but it's there.

The horizontal crack is a bit irregular as it slopes down from the window to the corner.

The ceiling is heavy texture and very irregular.

As for your first question about doing it yourself, it's possible, but it's not totally simple. You can't just use spackle on the crack, because it will open up again. The "easiest" fix would be to sand down a wide strip on both sides of the wall cracks, and then to embed tape, let it dry, and do a second or third coat to feather the joint out. Then you would have to re-paint with something that gave a heavy texture to try to make it all blend in. If you've never done work with joint compound, it's a skill that takes some practice and it would be easy for you to end up with the crack gone, but a more noticeable mess if you're not skilled with this. As for the ceiling, that's a tougher one because of the heavier texturing, and I can't tell you a good way to make this go away without a lot of work of the same kind.
The only other think I can suggest is that there used to be a product you could buy in a spray can that laid down a thin, flexible film that bridged the crack and then you painted over it. It might not work well for you given the size of your cracks. You could try spackling the cracks, which would close them up better, and then try the spray can approach. No matter what you do, though, you're going to have to re-paint.