Upgrading imac g4?

As I am unable to afford a new mac, I am looking to upgrade my Imac G4. Have no complaints with it anyway. I'm unsure as to what can be upgraded though(other than memory).

Machine Model: iMac
CPU Type: PowerPC G4 (2.1)
Number Of CPUs: 1
CPU Speed: 800 MHz
L2 Cache (per CPU): 256 KB
Memory: 512 MB
Bus Speed: 100 MHz
Boot ROM Version: 4.5.0f4
60GB Hard Drive
15 in. flat screen monitor
GeForce2 display AGP Card
TOSHIBA DVD-ROM SD-R1312:

I will upgrade the memory to 1 gig
I'm fine with the 60 gig hard drive
Not sure about upgrading display card.
Could go without the superdrive as I have an external DVD burner. (unless I can upgrade for cheap)
Would love to have the 17in monitor but am not sure if that's possible to replace on the imac.

Would appreciate any comments, suggestions, opinions.

Thanks in advance.

You can get an upgrade CPU if you want.

I couldn't find information on upgrading the cpu. Do you know of a website where I can look into this more? cpu, what type will work, ordering, etc?