Hello, SueAnne. I would definitely have your client send you the audio in MP3 format. It will really make your job so much easier. If you have to convert the recording, it can be time consuming and frustrating.
Do you know the webinar's file format? Express Scribe can load a lot of different formats, so it may be that your client's recording will be fine as is. Check out the file formats you can use with Express Scribe in its
HELP menu.
Good luck and enjoy your weekend!