Yes. Hit the V key while the track is selected. Then, where the audio clip is, make "handles" or nodes by double clicking the blue volume line that Vegas will insert. You'll need 2 handles in front of the clip and 2 handles behind the clip. You'll be able to then click/drag the area between the handles to raise the volume by as much as 6dB. You can also normalize an individual clip by right clicking, choosing Properties, and then checking the "normalize" checkbox.
Depends on what you're doing. As an example, the theme song for the Olympic Torch in 2002 used up 72 tracks in Vegas...because a lot of control was needed to properly mix the song. Vegas is more than just a video editor, it's an audio editor and mixing tool.
That said, if you're doing any kind of video work and you don't have at least 4 audio tracks, you're probably missing out on a lot of opportunity to make your video better with more/better/supporting audio.
Audio Track 1 : Ambient - could be voices in a room, traffic sounds, nature in all Her majesty. Yah know bird song, cows mooing and horses £arting!
Audio Track 2 : Sound effect - BANG! Crash Wallop! Or . . helicopter (sound) coming in over Nature in all its majesty
Audio Track 3 : Additional Music - something to keep the narrative bubbling along
Audio Track 4 : A Piece to Camera or the talking head. Now this could have been gathered and captured AT the same site as Nature .. etc etc . .. OR it could have been done in post and you reeeeally need to balance this with the tracks above!
Audio Track 5 : Further sound effects . .ticking clock OR rumbling
.. hey we aint even touched on 5.1 mixing yet! HAHHHA!
Now all these tracks you want. Now how you going to mix, sample and adjust if they are all in one track? - Well you couldn't - I'd be all over the place. Think of sound as we also think of multiple video tracks. You can also assign ALL these separate audio tracks with their very own mixing BUS - neat eh? Oh yes, of course, each track you can "rubber band" AND now use the Automation function to create fades and dims and UPS on the fly.
You got Spot's example of the Oly '02. My "example" is very close to what I just finished 2 weeks back.
Bottom line here is not to limit yourself with thinking you can't separate out and then re-mix sounds, music and whatever within post prod. Vegas will eat it all up . . . and then some!