you don't need to do anything that tank other than expand the top. Go to a Lowes/HD. etc and look around for what you want. Look in the garage sales, etc.. Find something, cut it to size.
Construction adhesive would easily do the trick w/o drilling. Though if you do, run a 1x4 - 2x4 under the top and bolt thru/screw into that. It will give you some lateral support and piece of mind (even though it's totally optional).
Its a nice looking piece of furniture, finish it off nice and it'll look great (and re-sell great when you upgrade).