Don't remove the dash.
I don't remember which of the 3 door actuators is which as far as their location, but you should be able to access different ones from either the left or right forward of the console or possibly through center with radio removed - to access from passenger side, you have to remove the glove box. There are some threads and maybe some How-To's discussing R&R'ing them - you just have to find those, but once you see the location of the actuator, you just have to get a wrench on the 3 screws - hard to reach, but do-able - helps if you have small hands and agile fingers.
Where did you get the part? If aftermarket, it may not work. Some people have made one good one from either the motor part from the aftermarket assembly and the rest from a bad original assembly, or vice-versa - I forget which. If you got an aftermarket assembly, we can dig up the thread about combining them if yours doesn't work.
'98 LXi - Later Concorde gages (black w/ chrome rings)/'99 LX - LHS gages (white) - HIR bulbs