Replaced the battery on the 2001 Bonneville earlier today. A few random notes:

Tools:
5/16 socket for the battery post removal
13mm socket with extendios to remove the battery hold down

Battery:
Hard to find battery because it requires special vents. Dealer prices is $180, only AutoParts store that stocked it in AZ was O'rielly, web-site cost of $149. Went to O'Rielly, they sold it to me for $119 (was super happy)

Replacement is super easy and clean. Pop out the bottom portion of back seat, remove old one and reinstall new one. No dirt to deal with, nothing in the way. Other than inspecting the terminals for battery corrosion, takes just a few minutes.

Is the replacement still a AC Delco or did they carry a different make of battery with the proper vents?

William,

Thats a great question. The battery is an aftermarket, specifically made with the vents. This is the third battery in the Bonneville. The first one was the original factory, second one was from the dealer, this is the aftermarket.

The neat things is the battery vent system connects better on the aftermarket than the factory replacement. GM downsized the factory replacement battery size, making the vents subject to disconnect. The aftermarket battery was sized to the original factory battery- the vents hooked up flawlessly. The aftermarket also increased the CCA from 775 to 875 (not that it mattered).