I want to take out the channel 9/19 switch and use it for an on/off for talkback. There are 4 wires on the switch, what do I need to do with them?

Just wire the wires that are closed by the switch in the normal position.

The center is common. each side is a different circuit. so you have pins like this..

- -
- -
- -

we will number them like this....

1 - - 4
2 - - 5
3 - - 6

Hope this will make sense. Its hard to explain with text only.
when the switch is in the down position, it makes 2 connect with 3, and 5 connect with 6. so pull off 2 and 3 and solder them together and the heat shrink them. then take off 5 and 6 and solder them together and heat shrink them. then take of the one that is most likely on the 1 pin, and clip the end, and heat shrink it to prevent it from shorting out on anything.

No the radio should always be in the normal position and you may wire the switch to what ever you want.