replace built-in RAM on the G4 ibook?

I just bought a "new" ibook G4;
Machine Model: iBook G4
CPU Type: PowerPC G4 (1.2)
Number Of CPUs: 1
CPU Speed: 1.2 GHz
L2 Cache (per CPU): 512 KB
Memory: 768 MB
Bus Speed: 133 MHz
Boot ROM Version: 4.8.7f1
Serial Number: 4H50500YS86
I want to upgrade the Ram, it currently has;
DIMM0/BUILT-IN:

Size: 256 MB
Type: Built-in
Speed: Built-in

DIMM1/J7:

Size: 512 MB
Type: DDR SDRAM
Speed: PC2700U-25330
The question is can I replace the 256 MB (Built-in) chip with a 512 chip.
Can this be done or is it soldered to the motherboard? What are my ram options with this model?
-RS