I just did mine, prior to moving in. I used a flat sander vs. the drum.
Someone had used a drum sander prior to me and gouged the floors in
many places. My floors had stain plus varnish on them, and I tried to
bring them down to the original wood. I was 95% successful. Luckily the
stain i selected did not show the areas where the previous owners had
gouged it with a drum sander.

Lots of work. Lots of fumes. Was worth it in the long run doing it
myself since I was on a strict budget. However, I would never
voluntarily do it again myself. If you have the funds, have a pro do
it.