There is a ton of variety in the restaurants in Montclair and the surrounding area. The town of Montclair prides itself on its downtown, mostly around Bloomfield Avenue, claiming it is where "the city meets the suburb." This area is filled with good restaurants, but they don’t cater to college kids and can get very expensive. Bloomfield Avenue is about three miles from campus, which is walkable on a nice day, but you can take an NJ Transit bus there, too. The food is pretty convenient, there is a lot of variety, and it’s good, but it's expensive, unless you just hit one of the fast food joints along the highway.
There are plenty of vegetarian options in the area. Veggie Heaven offers only vegetarian food, and other restaurants offer vegetarian menus. There aren't many local restaurants that advertise themselves as kosher, but there are quite a few synagogues in the area, so if you are interested in finding kosher food, it's probably best to get in contact with one of the synagogues to ask about options in the area. Overall, if you want something specific, you can probably find it with a little research, since there are so many options right in the area.