Woodworking question about finishes.

I've got a mix desk that I built out of red oak plywood and I finished it with Tung oil.
 
It's starting to show some staining and dirt from being touched and stuff.  I have been thinking about really reorganizing my hardware mounted in the desk so I think it would be a good thing to go ahead and refinish the desk while I have everything out of it.
 
I'd like to stain it black or as dark as I can get it.  I don't want a paint as I like the grain of the wood.  Can this be done without a ton of work since I've used the Tung oil?

bapu

Beagle
i'm definitely not the expert, but I'd think you'd need to strip it first.

Ok, but what about his desk?

(quacked me up......coffee out of nose and all....)
 

You might get away with applying a varnish over the cleaned/extracted and lightly sanded oiled finish, but it is pretty doubtful that you will be able to get the kind of stain result you want unless you remove the wood that has been saturated with the oil. That would mean extensive wiping with lacquer thinner to remove as much wax and oil as possible fist, then sanding to new/dry wood. On plywood, less so than on veneer, you risk going through the top layer with sanding, and then you would need to bond a veneer to  repair it or paint.

It should be easy enough to experiment on a non-visible area of wood, right?  Say, the back or the underside of any horizontal surface.  Just try wiping it vigorously with some paint thinner, put the stain on and see what happens.  If the tung oil was mixed with resins, you'll be SOL.  If not, the stain may or may not penetrate.  But either way, you're not going to have to put in much work to find out.