Well, I'm no expert myself, and I'm sure many people have many different takes on how to properly "quarantine" their orchids, but I will tell you my personal way (which has been 100 percent successful for me with many different types of plants).
When I bring home the new plant, I start the repotting process, which gives me an opportunity to look at the roots and leaves to check for any pests or fungus, etc. If you have to cut the roots, be sure your tools are sterile (wash them or hold a lighter to the cutter, etc) before cutting and sterilize it after as well to avoid contaminating other plants when you reuse it. After I have checked the plant and potted it, I put it in a different room in my house away from the other orchids and plants for a couple of weeks just to monitor it - plants that I have brought home in the past that DID have issues seemed to appear within the first week so I always thought a couple of weeks seemed adequate...
As far as the sink goes: I always clean my sink between each watering regardless JUST to be on the safe side. I had a stapelia gigantea that developed black spot and anything it came into contact with had to be cleaned, cut or destroyed. So better safe than sorry!
Once you find that your orchid is happy and pest/disease free, you're good to go! I keep all my orchids in humidity trays and fairly close together to help keep humidity levels higher, but again each person has their own way. My motto is if you have to question it, do it! (Ie: cleaning tools, washing sink, keeping plant quarantined a little longer, etc) Never hurts to be cautious and take all these extra little steps to make sure all your other plants stay healthy and happy, too.
And I'm sure it's not a question of IF you get another one, but when! Lol I started with one and now have 37. It's addictive!