Just did it, your description was very helpful, except my 98' S90 didn't have any screws. The plastic plate around the shifter pries off at the back as you suggested, and it also clips at four other places in fromt and on the sides.
had to take the trans mode switch out to get better access to the shifter bulb,
The most difficult was to slide the bulb back into the lightguide, and have everything back in place. Had they left another inch on the wires to the bulb holder it'd be a lot easier to do.
With some cursing, improvisation, and moving the shifter in all different positions I managed to put averything back together.
I woud like to seea green book procedure for this job. There must be a less painful way, or some special tool for it.

-michael