Staff should be like players, you could keep the staff but the wage will be higher everytime you renew, until they got age to retire or the contract ends.
Another fact is the random order you pick staff when you bid and more than one. You should pick in the order you bid.
I agree with the bid order, there's no real definition on who you get. Afaik its the lowest pick you get first, but im not 100% sure.