Could also try frameserving with AVISynth, then you can use delayaudio() and timestretch() to change the length or delay of the audio. Also no need to save out a wav that way as the audio is decoded to PCM on the fly.
If however you did want to make use of the wav just disable the audio in the AVI
avisource("whatever.avi",false), frameserve the audio wavsource("whatever.wav") and then dub the two using audiodub().