OTA HD reception is something of a black art. You might want to use AntennaWeb to figure out how far you are away from your nearest broadcast towers and what sort of antenna you're going to need to pull in your stations. You could also spend the extra bucks on quality RG-6 wiring, earth-grounded filter blocks, or even an in-line amplifier.

That said, DirecTV does carry HD locals (ABC, CBS, NBC, Fox, and I think PBS) for "east" and "west", but I don't know what the rules are about whether they'll let you tune those in. It might be that you need to live outside of the normal, official broadcast range or get an appropriate waiver from the stations. If you poke around the TiVo or AVSforum boards, you'll see various discussion on this.

For what it's worth, you can get a new HD TiVo for $600-650 (versus $1000 last year). If you go eBay, it looks like completed auctions for HD tuners are going anywhere from $130-$230. You'll also need a triple LNB dish, but DirecTV will give you one of those for free if you talk to the right person in customer service.

WARNING: if you get a brand new HD TiVo, there's a good chance you won't get the nice TiVo "peanut" remote control. These days, DirecTV is shipping out this completely awful slab thing. If you're buying a used HD TiVo, particularly on eBay, check which remote control you're getting.