You're almost there. There's a screw behind the kick panel. To remove the kick panel, pull the edge by the door jamb towards the center of the car. Therer's also a plastic screw where the lowe panel meets the carpeted side of the center console. Give that pastic screw a quarter turn. That should do it.
I guess your 89 has a passenger side airbag. I've only worked on my 126s with don't have passenger side airbags (87 and 91) so I can't help you there. If you're just replacing the blower motor, removing the lower panel will give you all the access you need.