Lexus Troubleshooting Questions? Ask a Lexus Expert
The 3.0 is notorious for valve cover leaks. This runs down the back of the block and looks like rear main leak at the bottom of the bell housing. I would have the valve cover gaskets replaced then clean and recheck for the rear main seal after you put dye in the oil. If the rear main is leaking the trans has to be pulled. The labor time on this is about 6 to 8 hours times your local rate.
These are not the easiest to do but compared to a rear main seal it is easy. The intake runner tube/housing has to be removed to get to the covers.