I'm not sure how different the 89 is compared to my 94, but all I did was get a thin screw driver and carefully insert it at the top of the lens and lift the handle slightly and it popped out. Change the bulb and pop the lens back in.
This is the procedure the Hemls manual recommends.
Disconnect the negative battery cable.
1) Remove door armrest
2) Armrest filler
3) Inside lock knob. Pry off (Snap fit on the rod).
4) Accessory trim plate
5) Power door lock electrical connector
6) Windshield wiper switch electrical connector
7) Two map lamp assembly retaining screws from accessory trim plate
8) Pivot pin from map lamp assembly
9) Bulb from lamp assembly