i want to see if these \"build a . . .\" flash sites (to support a user customized ordering process) are done using regular flash or Flex?
I recommend you start your development in pure Actionscript, that way you can make it as powerful as the language is, you should try Flash Builder, create a project, and then try with it.
i think it will be very easy, once you get the basics of AS3
Some As3 galleries and tutorials for you:
http://www.lemlinh.com/flash-tutorials-18-as3-image-gallery-tutorials-roundup/
http://www.flashmagazine.com/tutorials/detail/as3_photo_gallery/