Convert Sample rate...?

I once had a camera that had the option to record 4 ch of audio but only at 32k, two ch stereo was recorded at 48k.

Most video delivery is expected at 48k.

The answer to this isn't entirely straightforward. First thing I'd do is ask the client why the m4a had its audio at 32k samples - is there a good reason for this, or would he like it returned with (standard) 48k audio? If the client is happy with 48k audio, then convert his original audio to 48k, and have your session at 48k too, and then the final mixdown and re-encode will be correct without you having to do anything else.

But if the client wants the whole video at 32k, then the sensible thing to do is to convert your files to 32k too, and run the whole session at 32k - same thing applies to the re-encode. But I think it's the client's shout. If the client claims complete ignorance of the issue, then do everybody else a favour and convert it to 48k anyway!