No relay needed if the unit has TWO wires coming from it (this would indicate the relay is built in) witch is usually the case with viper systems. I don't have a schematic but, what I would do is this.
Once the wire is cut (the truck will not start), I then put my butt connectors on the alarm unit wires and crimp them. Then I'll put the other end of the butt connectors over the starter wires, and test the alarm to see if they are correctly hooked up. If it is not hooked the right way the truck will not start(no matter if its armed or not), I then swap the connection and re-test the alarm(the truck will only start when the unit is disarmed).
If you only have one wire from the alarm for the starter kill then yes you must use a relay, I'll link you to a starter kill relay picutre. Only use the "normally closed" relay diagram, and you will not need the resistor they show across two of the terminals.
http://www.the12volt.com/relays/page2.asp#sk1
Also a link for illuminated entry for ya, not sure witch is yours but on older toys it was a negative trigger.
http://www.the12volt.com/relays/page4.asp#ien