Are there any benefits to multivitamins? Any risks involved?

Minor. The typical american diet has more than adequate vitamins and minerals. If you think you are deficient you can consult with your family doctor. The only risk is the cost and the fact that vitamins have no regulation so it is not entirely certain that you are getting what is on the label.
Probable/small risks. There are benefits to multivitamins but surprisingly little good research. A recent study showed an 8% reduction in cancer risk using a vitamin that i consider to be poor quality; it's probable that a good quality supplement would result in a more dramatic improvement-see http://drrandybaker.Com/2012/11/11/vitamins-really-do-prevent-heart-disease-beware-of-bad-studies/ for my analysis&see comment:.