I understand the issue that you are experiencing setting up the Slingbox. I don't think that the sound issue is related to the source code; is the remote control working properly?
All the Directv satellite boxes work with the same code, so, if the HR model is not listed, you can use the HR20 or HR21 and the remote should be working. If not, look for the position of the IR cable; these two articles should help you out to determine why the remote is still not working:
For the audio trouble, I recommend you to check the position of the cables; if you are using component cables (green-blue-red + the audio cables white and red), you need to connect the audio cables to the second set of white-red inputs, have a look at this picture:
If you are using composite cables (white-red-yellow), they should be located on the first three inputs on the back of the Slingbox, on the gray area since they are inputs, not outputs.
Hope this helps.