Our family moved from Saudia to Qatar a few years ago. Final Exit is important and it involves a lot of things, like closing of your bank account in Saudi, closure of phone lines (land and mobile), announcement in the paper about you leaving and if anyone needs to claim something from you, plus settlement of your home rent and car (if any) alongwith any outstanding Traffic violation charges (if any). Plus your previous employer needs to give you an NOC and the iqama of yours needs to get cancelled. If at any point in time, you get a job offer from Saudia, it will be difficult for you to follow through with it.
Email your ex-employer and ask him how to go about it, as your re-entry visa has expired.