I just bought a 98 gs300 and I'm having suspension probs. I believe it's the lower control arm bushings, my question is what would I have to replace and how much would it cost

 

Your question is pretty vague. How did you diagnose the lower control arm and you know there are three right? Two in the front and one in the back. Plus a lot of other things could potentially be wrong that can make you think it's a control arm.

I'm not sure you'll get much help unless you give people more to work with.