overide switch for power locks

i own a 2005 xterra with manual locks and windows. i had a alarm installed with power lock actuators put in all doors with the relay setup off the alarm door lock /unlock signal wires which sends a neg. pulse. i would like to know how i can add a lock/ unlock switch. do i use a dpdt switch on the actuator side?(of course on the load side of the relay) OR can i send a neg. pulse on the signal side of the alarm module wires without backfeeding the alarm?

Using a negative trigger to trip the relays would be fine. You should probably diode isolate the wires to prevent any possible + feedback (ie...if it's a DEI system it provides - unlock + lock on the same wire...to prevent the off chance of hitting the switch at the same time as the system locks/unlocks)

You can find what you need to know about diodes here. Most (if not all) DEI door lock wires are green and blue. Just tap into these wires. I would not go through the hassle of a dpdt switch when you already have a relayed door lock system.