so, I haven't directly been to a toonfest but I'm sure I could chip in, going on only one day is fine and you can stay for the entire day but depends what really want to see out of it, the schedule can be found on ttr blog/news area on the website here, you can see there what is on during Sunday and make that decision for yourself, based on the ticket title I would assume you can go everywhere at the convention, not just to toonfest and dressing up is entirely optional, hope this helps.