I have a slow cooker recipe that calls for uncooked long grain rice but i want to use brown rice do i need to add more liquid or cook longer ?

As Trena said, it doesn't need more liquid, but it will need more time. I usually give white rice 2 hours on high and 3 hours for brown. Soaking the rice for a few hours will shorten that. Another trick is to heat the liquid you are using to just below a simmer before adding it to the rice.

I would actually say no to both. Long cooking dishes tend to overcook rice, so brown holds up a little better. If it goes 8 hours on low/3 hours on high, it should cook the rice just fine. If you're worried, I would soak the rice overnight before starting it in the morning. Even fast cooking recipes come out fine when I substitute white rice in this way.