Email them directly, they answered lots of questions for me. From what I've asked I think you need a qualified installer with special tools to do the job. You can also just phone a few installers to ask a few questions too.
HTH

You need a saw capable of cutting stone, usually a wet saw. You may be able to find a diamond blade hole saw and run water over the area you are cutting, but likely it will be easier to hire a stone shop to cut it for you.

Where is my head? I can't believe forgot -- I cut a 1 1/2" hole in my Silestone tile countertop to install a faucet. I used a hole saw I purchased in the tile section at Home Dept and made sure there was always a small pool of water where I was cutting. It took a long time, but made a nice, clean hole. My tiles are thinner than your countertop, only about 5/8" thick, so it will take more time, but it is definitely doable. Sorry about the first bonehead answer I gave. Maybe my brain is trying to block out my kitchen remodel to prevent further trauma.

Thanks aliceinwonderland. I'm thinking if I can find a place to do this that will do a small piece of silestone then I will have them do it. My problem is that anywhere I go, they have a minimum square footage which is way more than I need. Hmmmmmm you have given me some hope.