I wear a tri top and tri shorts. I throw on a skirt in T2 just before I head out for the run. I have never worried about or gotten chafed in a short race. I only put on chamois cream before the bike for an IM distance race, but everyone is different. If you're worried about chafing, try a more waterproof lube like Aquaphor. If it's a short race, you probably won't need to cover up too much to prevent sunburn- just put on sunscreen well before you swim.
When is your tri? The first one is so much fun- and then you just can't stop (kinda like Lay's potato chips- you can't do just one).