Finally figured it our after doing some searching and discounting erroneous information that I found on some other forums.
Step 1-- Key to #1 position. Ensure mode is set to FM radio.
Step 2-- Turn radio off (round button on bottom left of NAV), then back on.
Step 3-- Press and hold the Select button for approximately 10 seconds until the service menu appears (you will see the radio serial number).
Step 4-- Press the right arrow (left/right arrow button) repeatedly until "GAL" appears.
Step 5-- Press the numbered program button (1-6) that corresponds to the adjustment that you desire (1=least adjustment, 6=most adjustment)
Step 6-- Turn radio off to save settings.