how to repair the heater fan

This is tricky, as I've just discovered. I have a '98 Olds. The AC/heater fan was cutting out periodically. I was told it was most likely the blower motor. Replaced the blower motor. (cost: parts $47, private labor, $30.) The motor blows, but the air doesn't enter the interior. Problem appears to be a vent that isn't opening. Now I'm told that to replace or repair that problem requires taking off the entire dash board. I suggest that you might want to get an electronic analysis before hiring a repair shop.