Thank you!
also, do you know if your flooring's stained? is it brown or some other color that's not the color of...oak? if so, make sure you restain it before putting the lacquer on top. also, get wood filler if you have cracks.
so the process is:
1. sand
2. fill in cracks with wood filler (wood filler color to match final color of floor)
3. let filler dry
4. re-sand
5. stain (if necessary)
6. apply lacquer
so yes, you'll have to sand twice. the filler dries in a couple hours, so a one day rental should be enough, depending on the size of your room(s).