Answering your questions:

1. Everything in TN is rich with history, especially on religion. TN is basically the best place for a pilgrimage and of course to discover your roots. So come prepared with a camera and a video camera. It would help if you google the places you wish to visit beforehand so that you would know what to expect and marvel at.

2. Outside Chennai there are hardly any 5-star hotels. This is Asia you are talking about. What you can do is tell your agent to book you clean and good hotels - and inspect the rooms before you check in.
Five star hotels in Chennai would include Le Royal Meridien, Taj Coromandel, The Park, Fishermans Cove, Radisson, Taj Connemara, Trident Hilton, etc.

3. Watch the movie Thirumalai Thenkumari. Anyway, your itinerary will depend on the number of days you spend in India. See my next post for some suggestions.

4. TN is a heaven for vegetarian food. You can visit any restaurants and as long as it is air conditioned, you can be assured of hygiene. In order not to take risks, restrict your drinks to bottled water - ensure the cap is sealed. Refrain from any liquid that is not boiled including ice cubes.

5. Every temple is not just a temple, but also a shopping complex. Wear your biggest smile and start the bargaining session. Try not to bargain with the small time shops - be generous.