If they pitchshifted the audio, it's really your only way to go (since correcting that rarely sounds good).
If they didn't pitchshift, that method will preserve the 4% speed up, which I consider the biggest flaw in most PAL conversions.
Which since you have to re-encode the video to 480 lines anyway, re-encoding the audio as well doesn't seem a huge effort.
To sum up:
If the audio is pitchshifted (that is the tonal quality lowered so people don't sound like they're sucking helium)
-Resize/reencode to 720x480 @ 25fps
-DGPulldown 25 to 29.97
If the whole thing was just sped up:
-Resize/reencode to 720x480 @ 23.976
-DGPulldown 23.976 to 29.97
-Re-encode audio 25 to 23.976
And yes, BeSweet can convert DD5.1. If you use the command line it's "-ac3enc( -b 448 -6ch ) -ota( -r 25000 23976 )".
You can find the option on most BeSweet GUIs too.