After the battery is replaced, snap the case back together. Work around the rim from the front edge toward the heat vent. Squeeze firmly and make sure each plastic catch is engaged. Use the nylon spudger as needed to make sure each catch is closed before replacing screws.

Backup battery is a CR2032 Lithium button cell. Might as well replace it while you’re in there…

The case is secured by plastic hooks at 1” intervals. Use the nylon spudger and the opening tool to lever around the rim of the case. Start at the edge of the heat vent and work around the rim. Each plastic fastener will make a popping noise as they release.