The DB8 is going to be too directional. I'd back off to a DB4e which has plenty of gain while still offering a wide forward beam, enough to receive the spread of signals to the SW and expect the signal from WGGB, real CH-40 to 'sneak' in the back. (Start with an aim point of about 235°.)
If you find WGGB is not reliably received with the antenna aimed SW, you can add an Antennacraft Y5713 or Y10713 and a UVSJ combiner. Aimed at 218°, you'll get WTNH, real CH-10. (You may also get WWLP through the back of the Antennacraft at the same time.)
You can reuse the coax that was serving the satellite dish. You will need to remove any matrix-switches or diplexers, these parts may look similar to over-the-air splitters or amplifiers but will block OTA frequencies. Also, be sure the antenna does not end up pointing straight into the roof, many dish mounts are low enough that that can be a problem depending on which way the antenna is aimed.
I'm very happy with my SiliconDust HDHR tuners. They don't take up any space inside the PC, they tune any digital OTA signal and you get two tuners in one box.
http://forum.tvfool.com/showthread.php?t=820
If you have many sets to split to, you may want to add a CM3410 distribution amplifier just ahead of the passive splitter... but don't rush out and spend money on an amplifier until you've proven the need.
