Last Saturday I tackled the replacement process for my 2001 GS430 headlight bulb. I found a great thread here with detailed instructions, diagrams and pictures.

Some additional thoughts/pointers though:
1) The driver's side is indeed much harder than the passengers side.
2) The silver cap is held on by top and bottom clips and it can be removed by "rocking" the cap back and forth, with an action sort of like popping the top off a soda bottle (not exactly but close)
3) The clips holding the actual bulb are clipped onto a holder attached to the top of the fixture and need to be pushed back and apart to the outside to detach and back and together to attach.
4) The bulb itself has a notch which needs to be positioned up to fit into the fixture properly.
5) The last Item is a questions: I can not seem to get the outside cover to sit properly. When I turn it clockwise to lock it only engages on one side leaving the other side slightly ajar. I have tried several times with no success on either side (I disassembled the passenger's side to help me understand how the driver's side needed to be installed.)