I don't use this particular brand and model, but I do use a FW mixer to have multiple inputs for audio.
You can download the 1082 Manual from here:
http://www.zzounds.com/item--TASFW1082
Just beneath the picture, you'll see tabs. The Manual is in the 'Docs' tab. There's actually a few manuals all pertaining to this unit, you can download, all on this 'Docs' page.

With my unit, I received a disc with ASIO drivers. As farss taught me, I need to have my computer off and I have to power up my FW mixer first then turn power up my computer. Otherwise, my ASIO drivers disappear and I have to reinstall.

It was easy to figure mine out, once farss set me straight about my drivers. Also, this driver problem may not apply to all brands, but he was guessing with my "Helix" brand and he was right.

But I'll probably confuse you if I describe what I do with my unit, as your FW mixer may do things differently. But once I got going, it was incredibly easy.
You will probably end up assigning the inputs of the FW mixer to separate audio channels in Vegas. (Also, it never hurts to save a .veg of the set-up, once you figure it out, so, you're ready to record, by just dragging in that .veg.)

Also, although I have Vegas 8, I have not used it yet. It should work fine. I can't see it working any different from earlier versions, as far as audio goes.