HI. Unlike incandescent globes, old style regular bayonet style) it didnt matter which way you connected the globes +ve or -ve on the metal case or lead centre, it doesnt matter. With LED lights they are polarized which means one of the two leads out of a LED light is positve and the other negative . If you hook them up the wrong way they wont light up at all. That is the positive wire on the negative lead stops them working.
If you use LED lights as indicators they will flash at a high rate and you will need to slow the flash rate down by using a different flasher unit or a resistor with the led lights. No special switch is required.
Other than that , i am not sure.