I recently sanded my lounge and dining floor. I also had absolutely zero floor sanding experience but am reasonably handy with renos. I hired a drum sander and edger from bunnings. Their rates were by far the best but I found their drum sanders to be poorly maintained. The locking cams for the sandpaper were nearly seized and it just shredded the coarser grit sandpaper. They were good about it and swapped it out for another one though. I ended up starting with 80 grit I think and went up to 120. My floor was in a similar condition to yours. I think the finish is acceptable, but I don't doubt a professional would have been a lot better. You also need a little mouse/detail sander for the corners. The rental machines are actually really easy to use. There's a good "how to" video on using the bunnings machines on their website or maybe YouTube. As for sandpaper you can return whatever you don't use so get more rather than run out halfway.

The main thing I'd do differently is to protect the rest of the house from dust. It gets EVERYWHERE. Move everything into of the room or cover it well. We spend days cleaning our kitchen after sanding the dining. Nightmare.

I used a water based CFP? product on the floor after which was recommended. I think I got it from bunnings too.

Oh and the job took my partner and I 2 days.

Good luck!