You don't state what year your Sunfire is, so I don't know if there are any shrouds or other things blocking access, but this should be a fairly direct job.
Check out this tutorial: http://www.ehow.com/how_112575_change-cars-battery.html
Bear in mind, that if you don't know the security code to your radio, you risk rendering it useless when you disconnect the battery.
In order to wire the starter on a Pontiac Sunfire, you will need a jack, jack stand, socket set, and a torque wrench. You will need to make sure to remove the battery cables from the battery.
I need to know how to remove a rear wheel speed sensor on a 2002 Pontiac Sunfire
You have a bad alternator.
No, you do not have to remove the battery. Just remove the 2 bolts (1/2 socket) on the top and pull out the whole assembly. Then undo the big plastic nut and remove bulb and redo steps to install.
With a sledge hammer and a bottle of febreeze
You have to unplug the ground from your battery for 1 or 2 minutes.
To replace the dashboard lights in a 2005 Pontiac Sunfire, first, disconnect the negative battery cable for safety. Remove the dashboard trim panel by unscrewing any screws and gently prying it off. Then, locate the bulb sockets on the back of the gauge cluster, twist them counterclockwise to remove, and replace the burned-out bulbs with new ones. Finally, reassemble the dashboard and reconnect the battery.
On a 98 Pontiac Sunfire, the red color of wire goes on the terminal marked "B" on the starter. This terminal is located close to the battery of the vehicle.
The center console is held on by several mounting screws. To remove it from a Pontiac Sunfire unscrew all of the mounting hardware. The center console will then be able to be pried off.
It could be your alternator is going bad
The 1997 Pontiac Sunfire front bumper is held in place by six retaining clips and for retaining bolts. Remove the retaining bolts and pry outward on each retaining clip.
Remove the transmission oil pan