I have been to Munnar years ago, it is a nice place to visit. As it is a cold place, you should take sweaters and other accessories along with you. The main attraction in Munnar is when a flower "Neelakurinji" blossoms. It is a flower which blossoms once in 12 years. Then other attractions are tea farms, water bodies and so on. You can find Kannan Devan Tea Farm and industry there. You will get to know the technology of making tea leaves into tea dust. Seetha Kulam, is a place, where Sita, the wife of Lord Rama(Hindu God) has taken bath. This place is also in Munnar. You can also see a place where three water-bodies merge together. One thing you have to be careful about is the worms that suck you blood. It is very common there.
Have a happy visit.