Where are you getting chicks from? Most hatcheries will vaccinate the chicks for you, which is much easier than doing it on your own. I would personally vaccinate your flock, as the Marek's disease virus is everywhere. It is one of the worst diseases a chicken can get--it slowly paralyzes them, and there is no completely effective treatment. I, for one, would never want to have to watch my chickens suffer through such an awful disease.
YES! I had 8 chickens and they weren't vaccinated. One died and I will never know if it was mareks. I should have had a necropsy. Now I worry about my others. I wish I'd thought more about it. Now, either my birds have it or they don't and I won't know unless I have more that get sick.