I've made quite a few upgrade of armada E500:
6 or 12 Gb hdds to 30 gbs ones (Toshiba - ICN25N030ATDA04-0).
Only stuff you might have to do is upgrade the bios.
For the rest it is pretty straightforward (get the frame from the old 12 gb hdd and place it on the new hdd - plug into the laptop - done).
Hopes this help