Tivo upgrade?

Hopefully this is the correct forum to post a Tivo ? in.

I have the Hughes DirectV Tivo unit w 40 hr capacity. It is my understanding that the guts is basically a dedicated Linux PC w a 40 gig HD. Is that correct ?.

I have a spare 80gig hd sitting around, can I simply use a program like Ghost or Acronis to upgrade to that larger HD ?.

Will the unit automatically recognize & utilize the added storage capacity ?.

Will automatic updates from, DirecTv cause problems w the upgrade ?.

Thanks in advance,

If there is a better place to post this, let me know.