how long roughly will my bitch be in labour for.

0 to 36 or even 48 hours.  Your best guide would be to know what ehr female relatives did, but as in people it is infinately variable.

would there be any discharge and should i take the male dog away from her know that she has started panting

I would certainly expect mucus discharge, but until the first pup is born it would be clear.  You should have your bitch and her litter in a quiet place for at least two weeks and not allow any other animal in the same room.

thanks for your help.