I didn't see a tutorial for a drain and fill on the rear differential for the LS430, so I thought I would take some pictures when i did mine.
Make sure this is done on level ground, if one end is jacked up, you will not be able to fill it the proper amount. Also, it's a good idea to allow the rear to cool off a bit.
Here's a list of things you need:
2 quarts of 75-90w synthetic gear oil (it actually only needs 1.3 quarts)
2 Crush Washers (one for the fill plug and one for the drain plug) I got these at the Lexus dealer, but it's a very standard washer that you could likely find at a lot of different places.
Gear oil dispenser (these screw on the top and make it easier to put the fluid in since you're unable to get the bottle higher than the differential and use gravity
10mm Allen bit and ratchet to unscrew plugs. These are used instead of a traditional hex bolt.
Here is the label on the differential, synthetic only, 75w-90.
Here are the two plugs. the top is the fill and the bottom is the drain.
Unscrew the top plug first. That way you can inspect the level to see if it was low and if you possibly have a leak, and also, if it's stuck, you don't want to find out after all the gear oil has been drained out and it's then immobilized. Depending on how warm it was, a bit will likely dribble out when you unscrew the top plug.
Then unscrew the bottom plug
Fluid will then rush out. My fluid seemed factory fresh for the most part despite the mileage.
The rear plug has a magnetic portion and it did have some powdered metal, but no chips or shards of metal. I cleaned them off then reinserted.
I reinserted the bottom drain plug with a fresh crush washer and the factory recommended torque at 39 ft/lbs.
I then took the gear oil and used the above dispenser to fill in the top fill plug. You keep pumping until the differential fills and fluid comes out the fill hole. When one bottle is drained you move the dispenser on to the next one.
Then reinsert plug with a fresh crush washer and torque down to 39 ft/lbs. You should use approximately 1.3 quarts, when mine was all said and done it was 1.5 containers of gear oil.
I would rate this as an easy job, about the same difficulty as an oil change. It's honestly not something that needs to be regularly done on a vehicle like this, but I'm guessing most have never had it done a single time.