If this is not an issue you can sand off the old finish and or high spots then prepare the flooring by making any repairs or replacements of loose boards then thoroughly cleaning the floor.
Flooring you can place on your old flooring.
For one thing if you ever want to revert back to the original hardwood you can simply pull out the laminate and the old floor has suffered no damage.
A thin layer of joint compound suitable for indoor use spread over the old vinyl floor will patch up any gaps or dents and the holes left by removing the broken bits of the old vinyl floor.
In most cases you can install vinyl flooring on top of existing flooring.
If the hardwood floor is wavy you will need to do some work to level it out before installing your laminate floor.
Things needed cleaning supplies vinyl tile cutter vinyl tile adhesive trowel floor roller.
But you can do the same to prepare your floor so the new vinyl flooring will have a perfectly even surface to adhere to.
Installing a laminate floor over hardwood is a great option in many cases.
A good flooring to install over an existing floor is rigid vinyl core.