Since I already have a TESOL certificate, would that make it possible to have a shorter course or cheaper tuition?

Having a previous TESOL will not reduce the time of your course or tuition.  All prior learning and experience, whether that learning or experience was gained at a college, through personal experience or study, or in the workplace, is evaluated and awarded by the USILACS HESEAP Review Committee, via the USILACS HESEAP application.