How does one land — decelerate to a safe landing. The amount of fuel required to fire a mars retro rocket is many times that on earth. Then you need to lift off.
Getting to mars is not the issue — landing and taking off is the major challenge.
That machinery can be sent gradually and ahead-of-time.
"Just because the raw material is there doesn't rocket fuel make"
No, but it means that such fuel is at least possible.
"I'd be hard pressed to say that oxygen is plentiful on Mars"
The current understanding is that there's millions of cubic meters of water ice on or near the Martian surface (with even more suspected further beneath the surface). Sounds pretty plentiful to me.
So yes, both of those things are plentiful on Mars. Maybe not to Earth standards (or the standards of, say, Ceres or Enceladus), but certainly abundant compared to our own moon (at least as far as current information tells us).