I don't have experience with the Dual Top (only the single), but it appears to be identical (albeit with 2 pump slots) as the X-TOP. So it should perform the same, and EK's stuff is generally high quality.
Mounting the top to the pump is very easy, unscrew the old top, and you have 4 pieces (pump, bottom part of the top, top part of the top and O ring) to fit together. Anyone can do it, don't worry about that side of things.
Mounting in the case may be interesting, as its quite a large block, but the same rules apply as without a top, suspension or insulation from the case is required. Don't expect the top to work magic with the noise, you'll still need to de-couple it from your case.
Thanks for the answer
Hopefully someone can jump in who has experience with both
Cause I really would like a comparison in noise between the 2 (otherwhise I can just as well buy 2 of the single tops for almost the same price)
About the mounting:
I was wondering about using the supplied mounting system to mount it in a 5.25" drive bay... But of course I would only do that if this gave the best possible accoustic result... So I hope some also has experience with that...