Hi. I'm new here and I just bought a 2003 LS430. The car is in excellent condition. The issue I have is the drain for the moonroof leaks into the interior on the left side. It looks like the headliner has to come out to fix this. Does anyone have experience in this area?

 

Sounds like the rear drain hole is badly clogged and completely blocked. You need to clean it. This is about LS400s but things are mostly the same. To do it quicker, I used a bore camera to find the drain hole and tried a pressure method using a compressor, a pipe and some soap water.
You can find my method at the post #8.

 

I addressed the leak in my headliner. I took the headliner down and found the drain tube off of the fitting. Someone had been in there to do some work and left the tube off. I re-attached the hose and secured it with a #4 clamp. I put it all back together and poured about 4 ounces of water into the rain channel and watched it fall out behind the left front tire. All is good, now.