Dual Channel DDR SDRAM
128-, 256-, 512-MB or 1-GB
128-MB DDR SDRAM
NOTE: Between 32 and 64 MB of system memory may be allocated to support graphics, depending on system memory size and other factors.
PC2700 (333-MHz) or PC3200 (400-MHz) DDR SDRAM
The old dimms are simply held in by retaining clips at the ends of each dimm slot. You simply press down on those just enough to see one end of the dimm itself start to come up in the slot and grab it by the top edge avoiding the contacts while having your arm resting against the case to prevent any possible esd problem.
With the new dimms you have to handle them in the same fashion in reverse by first seeing yourself grounded to the case in the same manner evenly inserting each new dimm down firmly until the retainers click into place. Verify those have done that before closing the case up and powering on the system. If no damage or defects with the new memory are seen you shouldn't hear any odd beep code.