I have an old-but-not-that-old pedestal iMac from 2003. It currently has a 80GB HD, 1.25 GHz PowerPCG4 processor, a mere 512 MB (2x256) RAM, and it's currently running Mac OSX 10.5.8. Are there limitations as to 1) the max size of a new hard drive that I can get for this marathon machine and 2) the most RAM. Thank you.