Ok, sorry forgot about the fact that your shades operated from multiplexer/spyder system. Again, I do not know which brand of motor/limit system you have, but should be about the same. The drum that your shades roll up/down on has a barrel motor inside. This is a DC motor with gearing that turn a clutch/drive assembly. The polarity is simply reversed to go up or down. The limit switch is either built into the motor itself or attached to it on the fix side (not drive side) of the motor. This enables the upper limit and lower limit of the motor travel (shade movement up/down) to be adjusted using a special tool.
In most of the applications, to remove the motor requires taking the valance down, remove the bracket then remove the drum roller with shade. Unrolling the shade material to expose a set screw that holds the motor in place. Then simply pull the motor out of the drum. Once the motor is out, you can either replace the drive motor (easiest) or disassemble the motor housing a replace the limit switch and/or motor assembly. Care is necessary when putting the motor back into the drum making sure the drive gear matches the drive insets in the drum.
When you determine which brand and type motor system you have, there are good YouTube videos that show details on this process.
Good luck,