Sup Bro,
If its on the driver side, it's going to be tight (mainly due to the battery in the way).
First off, you'll need to pull the plug on the bulb (3-way connector).
Second, the grommet that seals the H4 bulb and the headlamp housing will need to be removed to get the H4 bulb.
Three, Once the grommet is removed, you will see a locking-pin housed in the head lamp housing that needs to be release (this pin lever is spring loaded to latch the bulb to the bulb opening).
Four, the bulb is now fished out of the limited space between the battery, PDB (power distrbution box (Main fuse box in the engine bay)) and the back H-lamp cover/opening.
Now you are ready to place the replacement bulb back into the assembly.
Just repeat steps four to one to reassemble. It should take nomore than 15 minutes. Just remenber not to touch the bulb glass..... if so touched, the life expectancy is shortened mainly due to the grease from your fingers.
You can find illustration on how to do this procedure in the 2000 Solara owners manual under bulb replacements or search for bulbs. Best of luck Bro...
Peace,
-G