take it to the Toyota dealership and ask them to replace it
It's an easy job, details can be found here: http://groups.msn.com/Sorensonbrian/yourwebpage.msnw
Pretty sure its the same as the 2000 Toyota echo, see related link.
when it breaks
about $1500 AU
most likely in the evap canister.
$1500 to $2000
You can replace your 2003 Toyota Echo antenna. Remove the antenna retaining nut. Remove the cable from the bottom of the antenna. Reverse the process to install the new antenna.
$250-300
go to dealer
You can access the bulb from the trunk area (from behind). Just remove and replace, should be straightforward.
Oil control valve. This might help even though its not an echo, its very similar: http://www.newcelica.org/forums/showthread.php?t=249837