take it to the Toyota dealership and ask them to replace it
Pretty sure its the same as the 2000 Toyota echo, see related link.
when it breaks
about $1500 AU
$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
$5
You can access the bulb from the trunk area (from behind). Just remove and replace, should be straightforward.
How to open hood on Toyota echo
The fender must be removed so the light will slip out