Can I use a Nissin Di466 flash with my Nikon D3100 via a wireless flash trigger?

Will the iTTL function be available with this setup?

Added (1). Thanks Luke. What I want to know is whether I can use the cheap flash triggers (found on ebay @ around 25 USD) with this setup and make use of the iTTL function.

No, unless you have a special wireless flash trigger such as the expensive as hell pocket wizards. Just get the cheap ones IMO, you don't need to be "that" professional. Manual is also the way to go for flash / studio photography.

You won't be able to use the iTTL function.

You can set the flash manually when used off camera.

How do you know how much power to use?
1.use a flash meter
http://www.sekonic.com/Products/L-758DR/Overview.aspx
2.take a picture, look at the LCD screen and adjust
3.use guide number maths (it is a little too much math for me)
http://strobist.blogspot.com/2007/12/guide-number-your-free-flash-meter.html

You'll have to use guide number maths to decide how much power you need.