I think it's fine to take a day off. I work out with a personal trainer and if I tell him that a particular body part is really sore, he'll often have me take it easy on that muscle group. For example, if my legs are really sore, we'll focus on upper body stuff. Recently my abs were ridiculously sore, so we just skipped abs altogether for that workout.
In your case, your whole body was sore; you couldn't just focus on a different muscle group. So I think taking a day off to give your body a rest was an appropriate response. A little soreness isn't a bad thing and it is sometimes okay to just push through it, but you know your body better than anyone else. If things really hurt, it's time for a rest. It's sounds like you put in a great week of workouts and got a great workout from FitTV. Plenty of people who put in that level of exercise would have taken Sunday off whether they were sore or not. Lots of people take at least one day off per week and many fitness experts recommend it. I don't actually take a day off but I have one day where my exercise is much lower in intensity than the rest of the week.
In terms of knowing when you are overdoing it, I think the general signs are chronic pain (soreness that persists for more than a week), pain in your joints (rather than your muscles), frequent illness (coming down with a lot of colds, etc.), and feeling fatigued all the time (not just when you have just finished exercising). There is some great information on overtraining
Also, I want to point out that I'm not a "fitness expert" by any means, so take my response for the amateur and completely unqualified opinion that it is.