Access to the upper section of the rear lights is through the speakers.
You don't say what year the car is but this is for the 2000 model:
Tail light bulbs (wagons)
1. Direction indicator
2. Brake light
3. Tail light
4. Back-up light
5. Tail light / Rear fog light (left side only)
All the bulbs in the tail light unit are replaced from inside the cargo space as follows:
· Turn the ignition key to position 0 and switch off the lights.
· Remove the upper panel of the tail light unit by using a screwdriver (1) and/or the lower panel by first removing the side floor cover and turning the plastic screw at the bottom of the panel to release it.
· Press down catch A (upper section) * or press catches B toward each other (lower section) and take out the bulb holder.
· Leave the connector and cables connected to the bulb holder.
· Remove the bulb by pressing it inwards and turning it slightly counter-clocKWise.
· Insert a new bulb into the bulb holder and reinstall the holder in the tail light assembly.
· Check that the bulb works. Reinstall the cover.
* The optional speaker (see illustrations 2, 3)) must be removed first to gain access to the upper bulb holder.
And this is for the 2001 onwards:
Replacement of bulbs in backup light, rear parking lights and rear fog lights[*]Switch off all lights and turn the ignition switch to position 0.[*]Open the access panel.[*]Remove the sound insulation behind it.[*]Twist the bulb holder counterclockwise and remove it.[*]Press the bulb inward, twist it counter-clockwise and extract it.[*]Fit a new bulb.[*]Fit the bulb holder in place and twist it clockwise.[*]Refit the sound insulation and put the access panel back in place.

Replacement of rear turn signal and brake light bulbs[*]Switch off all lights and turn the ignition switch to position 0.[*]Using a screwdriver, carefully pry off the speaker grille.[*]Pull out the red tab in the speaker.[*]Then press on the black pin above the extracted red tab and twist out the speaker.[*]Twist the bulb holder counter-clockwise, and withdraw it.[*]Fit a new bulb.[*]Fit the bulb holder in place and twist it clockwise.[*]Refit the speaker and press in the red tab.[*]Press the speaker grille back into position.