To make symbols fully editable you need to 'Break Link to Symbol'.
In Illustrator 10, once you have the symbol in your work area, simply right-click and choose 'Break Link to Symbol'. This is currently broken in Illustrator CS so you will need to click on the 'broken chain link' icon at the bottom of the main symbols palette (this can be enabled throught WINDOW | SYMBOLS.
After you have broken the link to symbol you will need to ungroup the symbol - right click and choose 'Ungroup'
Please let me know if you have any problems making this work,
Regards,
Adrian