stain over finished cabinet.

I have a bathroom vanity (oak) that i was to retain with a grayish tint to it. I am sanding it down and using the surface prep to clean it. Even with sanding, there is still a lot of color. It was originally stained provincial, I believe. I want to leave a little of that color on and use the graphite stain to show on most of the grain. How far down do I need to sand and/or once I get it clean with the surface prep, will the graphite stain adhere to? Am I wasting my time trying to re-stain it? Since it is solid oak, I didn't want to paint it.
It is presently in my garage upside down (easier for me to reach) on cinder blocks.