[Cypher]

Hi I'm new to macs and have dabbled a bit with them but I am unfamiliar with the file systems and operation. The problem I have is that my friend has an inherited emac that she got from a family member who did not take care of the disks or anything and my friend doesn't have the cash to purchase Adobe CS again and is a freelance graphic artist. The system was upgraded to Tiger.
The screen has begun to flicker and shake while she is working and we are afraid it will go out soon. I have an inherited G3 that I replaced the dead super drive with a 3rd party DVD drive to bring the system back up and install Tiger.
Is it possible for me to put the HD in the G3 and get back up and running or is it possible to move folders over to the G3? Thankfully I just got her to put her files onto a 500gb backup external drive a few weeks ago.
Also while I'm here what is a recommended imaging/backup software for the mac?
Thanks in advance for any help.
Cypher