Transfer Question

I have been using an old G5 tower(PowerPC processor old) for the past couple of years. Earlier this week the computer would not allow me to get to the log-in screen (It seems to stall at the grey screen with the apple logo). I was planning on replacing this computer any ways so I went out an purchased a new IMac as the replacement. My question is, can I still transfer the old files from the old computer to the new computer using a fireware cable (think this would treat the old hard drive as an external hard drive), assume there is not an physical issue with the hard drive but an issue with the operating system. I am also planning on purchasing an external hard drive due to this issue (I have learned my lesson).

Thanks for an help.