Need to Replace Hard Drive

My Premier (TCD-746320) developed a case of "Green Screen". After several cycles of waiting the required 3 hours and restarts, it is clear that it has died. Is there a way to replace the hard drive with a clean image? I know nothing about the workings of a TiVo, but work with computer hardware and Windows OS at the network level, so I am reasonably competent to undertake such a task. Can anyone supply directions, necessary software and an image?

Thanks in advance,

Mark