I'm pretty new here and even I think if you buy that cabinet you should just enjoy it the way it is! If you've been searching for a while you know how hard it's getting to find original DK caibnets in such good shape.
I've been doing the math myself a bit, and building from scratch in this case really shouldn't be ridicoulsly more expensive. To convert you'd still need to buy new graphics/vinyl/marquee, build a new CP or modify the current one. You'll need a computer either way for MAME and Fix it Felix, Jr.'s browser version, and an IPAC to encode it.
The only thing you're saving on is wood, t molding, and paint. (and some other small things I suppose)
Once again, new here, so I could be completely wrong!