RAM is never a guideline of what video card will work where or even how fast it will be.
Case / motherboard constraints, power supply are the main thing you need to look at and list. I've worked with those systems, they are not very speedy, so don't plan on playing many games with it. It also looks like it only has an AGP video card slot, which means you are pretty much stuck with finding something on the used market or probably paying way too much for a new one.
"Removing the AGP Card
A 1.5V low profile Accelerated Graphics Port (AGP) card may be
installed in the AGP slot on the system board. To remove the AGP
card from the AGP slot:
1. If you have locked the Smart Cover Lock, use Computer Setup to
unlock the lock.
2. Turn off the computer properly through the operating system,
then turn off any external devices.
3. Disconnect the power cord from the power outlet and disconnect
any external devices.
4. Remove the computer access panel.
5. Locate the AGP card on the system board.
6. Lift up the slot cover retention latch that secures the AGP card"