I do all my own oil changes and here is what is involved ['99 RX300]
1: Auto transmission and front differential [15000 miles]:
Only use Toyota Type IV. Its available in 5 litre cans at the dealership. Open both the transmission and differential drains. The differential is seperated from the transmission by an internal wall; there is no front differential refill hole.
2: Center viscous differential [30000 miles]:
You will need a 22/24mm box wrench. I use Mobil1 Synthetic Gear Lubricant for the refill.
3: Rear differential [30000 miles]:
I have the [relatively] rare Torsen differential, which is under-utilized. It would be better as the center differential. Again, I use Mobil1 Synthetic Gear Lubricant
4: Engine:
Mobil1 5W30 [10000 miles] and Mobil1 Oil Filter [5000 miles]
Don't forget to use new drain hole gaskets from your Lexus parts counter. The gaskets are all different!
Also, when refilling the center and rear differentials you will need to buy a lubricant gun with a flexible nozzle to get aroung drive shafts, etc. This enables you to get the new lubricant in using pressure.
Good luck!