http://www.newegg.com/Product/Produc...82E16815116631
this is probably the best deal out there. Hauppauge makes a very nice tuner. this package comes with the MCE remote, and an IR blaster. the IR blaster sits in front of the direct tv IR sensor, and windows transmits the signal from the computer to the direct tv box. i do believe though that Media Center is required for this guy.
another good place to start is
www.hardforum.com . they have an HTPC section that has guides to answer pretty much every question you have, along with a knowledgable crowd. and if you want to get even more technical try out
www.avsforum.com . these guys have info on pretty much everything HTPC related.