Help me with using an external display with my iMac

Hi this is my first time doing this, but I want to connect my iMac to my LCD TV via HDMI, but my computer only has a mini dvi port on the back. What cables do I need and is my iMac capable of outputting to 1080p?

I have the baseline late 2006 iMac (5,1) with ati x1600 card and my current display resolution is 1440x900.

Will I have to have both monitors on or can I just have the LCD TV be on and the iMac built in monitor be off?

Thanks for the help.