The thing is that flash is a compiled language, so what you see here is the ascii representation of a ‘program’ you can’t understand. In fact, even your browser can’t if it doesn’t have the flash plugin installed.
So you wont be able to modify the swf file. However, you can try to understand what it does to try to alter or fake it.
If you use Firefox, you can find some very useful informations in the network tab of the developer’s tools (F12).