You can look this up on the web. I just googled and look at WEBMD. According to that site, if it you take too much long term, it can have affects like, constipation, upset stomach and kidney stones. I don't see anything about taking it for a short term. If you are concerned, make sure you drink plenty of water. WEBMD suggests 2000IU per day for an adult.
You shouldn't be taking any without taking an inexpensive routine blood test to determine your baseline vitamin D levels.
It's very hard to overdose on vitamin d, the recommended daily amount are actually significantly lower than what your body actually needs on a daily basis. In the extremely slim case scenario that you really overdosed- you'll know. At that point you should contact a medical professional.
That is true, yellowbirdhead, however the test is very inexpensive in the United States, often given as part of n annual check-up, and you know exactly where you are.