How to remove movie clips in AS3

I’ve attached a small example of what I’m doing. The finished project will have a main menu with buttons to 6 pages with 6 maps on each, and 4 other pages.

The problems I’m having are:

1.) I’ve attached movie clips (map graphics) on frame 5 accessable with buttons on frame 1. But when you go to the maps (frame 5) and roll-over them, and use the BACK button to return to the main menu (frame 1) the maps are still there.

2.) In looking for a solution to this I’ve read that even if I make the maps not visible they are still there, and will add to the size of the file if they are loaded over and over again. I’m thinking I may have done this all wrong and when the project is complete it’s going to be a big mess. How can I simplify it?

Any help appreciated. Thank you!