Extending PCB switches and LEDs
Is it recommended or even possible to piggyback 24awg wire to the solder joints on the PCB


Recommended: no. Possible: yes. 

As in, you'd get something of poor quality suitable for lab/hobbyist purposes only. AWG 24 sounds a bit overkill, as there won't be any larger currents. Thinner wires would be recommended as that will be easier to soldier onto the SMD pads. Make sure there is some mechanical relief so that if you pull on the wires, you won't directly strain the soldier joints. Hot glue or similar could be used for this.

If the white connectors on the board are intended for switches, then naturally use those for the switch. Looks like some manner of Molex or JST connectors. You might need a crimping tool.


  For the switch, would the second remote switch still work or would the pcb mounted switch interfere with its operation? 


If it is just a dumb switch, then yeah you could mount 2 of them in parallel and either will work. The only thing to consider then is de-bouncing characteristics, which may be different if the switches are of different types.


  I need to relocate the MicroSD reader from the pcb to the dash mounted control panel. Im probably going to need to extend it about 2m. Is that going to affect my write speeds?


It won't likely affect speeds, but most definitely EMC. I take it this is PCI or a similar high speed bus? You'll have to read up on recommended wire lengths for the given bus, at the used baudrate. All of this assuming that the bus is already terminated in both ends, otherwise you'll have a 2m stub and that's unlikely to work.

And in the end, if this is a commercial product to be installed in cars, you have to go through various EMC and radio tests or the product will be illegal pretty much anywhere in the world.