I would suggest getting started with an antenna install, then once you have a reliable set of signals to work with, turn your attention to accessories such as the PVR/DVR and perhaps the convertor box for an older analog TV.
I like the suggestion made by @teleview, to use your chimney as the base for your antenna installation. A good quality chimney mount kit will easily hold a 10' mast section with no guy-wires needed. Putting the antenna up high, clear of smoke from the chimney will make the antenna last longer and improve your reception compared to a lower mounting.
If you are intending to record at some point, you'll want to err on the side of reliable signal quality. The HD7000R suggested earlier is a good antenna, but if you opt for a bit larger antenna such as the HD7080P (or even larger 7082 & 7084), you'll add insurance against signal dropout caused by close-in foliage.
As far as mixing computer and TV goes... The input of the HDHR is a coaxial antenna connector, the output is a 100 Mb/s Ethernet Port. The interface between the HDHomeRun tuner and a traditional TV is a computer with enough processing power to handle HD video. I have found through professional and personal experience that Wifi connected devises don't perform nearly as well as the same components connected via wired Ethernet.
As an example of the PC 'horsepower' needed, my wife's laptop (a Gateway NV59C) is able to handle the task. I would expect most computers that originally shipped with HDMI output from the video adapter, and especially those that included a Blue-Ray drive, would be up to the task.
My wife's laptop shipped with WIN-7 Home Premium. That includes the Windows Media Center which is able to act as a PVR/DVR. It knows how to use the SiliconDust HDHR as well as other PC attached tuner such as Hauppauge products. Sorry, I have no personal experience with the MAC version of software, though I'm confident that it's also quite capable.
I use an old XP box to record to disk. It has no HDMI, but handles 1080i video at the highest broadcast rate when I choose to watch recordings or live TV on it.
http://forum.tvfool.com/showthread.php?t=820
http://forum.tvfool.com/showthread.php?t=12717
http://forum.tvfool.com/showthread.php?t=2882