It's pretty easy as the 2003. Follow the steps in the link below.
http://articles.dashzracing.com/chevy-silverado-2003-2004-2005-2006-diy-tail-lights-installation-chrome-black/
remve the tail light they are on the back side.
The dash light fuse gets its power from the tail light fuse. If the tail light fuse blows, you won't have any dash lights either.
It should if it is the round body style such as 2001 or 2002.
remove tail light and reach through
Remove the tail light housing and replace the bulbs.
Well If you unscrew the taillight from the car take it off you can change you tail light bulbs
you don't replace the tail light you just replace the bulb in it
From the inside, behind the panels.
To replace the tail light on the trunk lid of a 2001 Cadillac STS, first, open the trunk and locate the access panel behind the tail light assembly. Remove the screws or clips holding the panel in place, then disconnect the wiring harness from the tail light. Twist the bulb socket counterclockwise to remove it and replace the bulb if necessary. Reassemble everything by reversing the steps, ensuring the tail light is securely attached and the wiring is properly connected.
pull back carpet around the taillight. It should be three plastic caps that unscrew and pull the light out, disconnect the bulbs. Replace with a new tail light.
Open the tailgate and look at the sides opposite the tail light sides. There should be two screws. Unscrew them. You should be able to pull the lenses straight out after doing this.
Read more: http://wiki.answers.com/How_do_you_replace_the_tail_light_in_a_2000_pontiac_sunfire#ixzz1Nur0XSlq