Shortening and Looping clips is easy... just click-and-drag near the center of either of the clip's edges.

Having audio and/or video tracks fade-in is easy.  You click-and-drag near the top-left or top-right of a clip to adjust the time over which the fade takes place.  (By right-clicking on the top of the fade-area, you can even adjust the spline-curve the fade follows.)

(click image to view a larger version)
If you need to cross-dissolve between clips, just drag two, adjacent clips on top of one another and Vegas automatically cross-dissolves the overlap between the clips, (letting you change this at your whim by moving and/or shortening/stretching the clips)!