Flash gives you far more power in your web designs than just an intro page bud. I design entire sites in Flash and used to use it to develop childrens software in 2000-2002. The hardest part to get under control is the action scripting. I use Flash 5 and would absolutely recommend getting the Flash 5 Bible to go with it. Great section on action scripting commands. Flash-kit is also a must have IMO for some serious development. Well, that was before Adobe bought the Macromedia Development Suite (Flash, Freehand, Fireworks, and Dreamweaver.) I still use that suite for any development I do.
There really is no easy way to explain using Flash. It all comes down to the actions you place on the time-line, or the movie triggers you use. Spikes gives a good resource for looking at previous work (especially the actions used) but you will still need a minimum knowledge of action-scripting to make your additions to, or subtractions from, the movie you choose to use.
Another thing that could be done is to find the intro movie you want to use, but change the calls to your graphics, rather than the graphics used in the movie example. Or delete those graphics from the movie library and place your own in it, named appropriately.
ReDhAwK