The SD signal came from one satellite (101). The HD receiver will need to get it from at least 3 satellites (99, 101 & 103). This needs an oval dish (Slimline) and a 3 or 5 sat LNB. You can get a legacy 5 sat lnb. This has 4 coax cables coming down and can use a multiswitch to route it if you have more than 4 tuners. I would not suggest this route. The latest setup uses the same Slimline dish with a SWM LNB. This uses one coax from the dish into the house and then splitters are used to send the signal to different receivers.
I realize that this is a requirement here to question why anyone would want a Tivo, so I'll do the dance..
I have a genie ( with2 pups), 1 Tivo HD already, SWM connected. The Tivi will be on a seperate dish (for reasons having nothing to do with connections, networking, etc.)
My wife hates the Genie.
No that's an understatement, no Tivo no Directv.
As for me, the genie interface is not always intuitive, its runs a bit slow (it is a 34), but its "ok".
After joining Directv in 1993, I've had the fun of playing with several receivers, dishes, etc., my dream setup would be a networkable Tivo.
But if wishes were horses...