Lighting advice for planted tank beginner

[Xielos]

Hi there everyone. I've had a freshwater tropical tank up and running for the last 4 years or so (barring that time the heater exploded). Its been a fairly basic setup, normal gravel, standard florescent lights, plastic plants and your motley assortment of angelfish and otto cats. I've recently made a friend with a beautiful planted tank, and along with some extra income as of late I felt inspired to do the same with mine. Heres a run down of the tank as of now:

-72 Gallon bowfront
-RENA FilStar XP3 Cannister filter
-Some natural driftwood, plastic plants, normal gravel, ceramic decoration
-Standard 32 Watt fluorescent lights x2
-Single air pump/air stone making a few bubbles

Residents:
-Two medium sized Angelfish
-One otto cat (that I know of, the other 2 have been MIA for months, I spotted this one for the first time in just as long last week)

So I have two main areas of concern: lighting and substrate. Will I need to replace my gravel with something else if I'm going for just a lightly planted tank? What should I replace it with if I wanted more plants?

What lighting will I need for a tank of this size? Will I need to worry about water temperature? The tank currently gets many hours of indirect sunlight a day, as it is across the room from two large sliding glass doors. Temperature is usually around 80F, with a heater in case things get cold (Central Florida, not often). Will I need a new hood?

Thanks in advance for your advice. If theres any obvious beginners guides I missed, I'd love to read them.

[Jaykit]

Will I need to replace my gravel with something else if I'm going for just a lightly planted tank? What should I replace it with if I wanted more plants? No, you don't need to replace the gravel. If you want, you can add flourite or another type of enriched soil but it isn't needed.

What lighting will I need for a tank of this size? Depends, are you wanting high or low light plants? Do you want to add Co2? 2 wpg is the deciding factor. Less than that you can grow any low light plants and some medium lights plants. Above that it is recommended you add co2 and you can grow anything you want. http://www.plantgeek.net/plantguide.php is a good site to see what you want to/can grow.

Will I need to worry about water temperature? It has never been a concern of mine to adjust temperature for my plants. I set it for the fish I have in the tank and the plants grow like crazy so it can't be hurting them.
Will I need a new hood? Most people go with glass tops so that as much of the light from the fixture penetrates into the tank. If the one you have works then "why fix what isn't broken".

[Xielos]

Thanks for the link, exactly what I was looking for!

So if I want to keep low/medium light plants and not have to mess around with CO2, 2 watts per gallon is my light limit? At 72 gallons, I'm, looking at no more than 144 watts. Does Kelvin rating matter? Should I go for light bulbs advertised as "Daylight" bulbs?