First time making fudge. Will it be okay if I forgot to add vanilla?
Vanilla is not an essential ingredient in fudge. The essential ingredients are sugar (or an equally calorie-rich sugar substitute like corn syrup), milk and butter. Everything else you might find in a fudge recipe is just added to modify the basic flavor, texture and/or color. There are lots of fudge recipes around which don't use vanilla at all (it's a treat which is very open to experimentation in general).

So if you don't add vanilla, it won't taste like vanilla, but that doesn't necessarily mean it will taste bad, have the wrong consistency or behave differently when cooked and cooled. It's certainly worth a try to complete the recipe, even if just to collect some experience with the non-trivial phases of making fudge which are going to follow.