Sacrilege springs to mind!
Why not strip it back to its natural finish and wax it, it will look superb. Oak is so beautiful in its natural state I just dont understand why someone would want to paint or gloss it!
However, if you insist I would recommend at least sanding it down or you just wont get a smooth finish and it will look ghastly.
Snap Mrs_Pegasus, I've just typed out a similar reply on Pejay's previous question. Oak is our favourite wood/furniture & we wouldn't dream of painting over it! Sacriledge certainly is the only word for it.
If you must change the colour, perhaps you could sand it down, apply a coloured woodstain, then varnish it. At least you'd see the beauty of the woodgrain. Painting oak.. OMG, sounds like the 60's and 70's when people put hardboard over nice old doors.