Even if they are an ex-staff member, if the warns were false you should've dealt with them when it happened, otherwise there's nothing anyone can do. You're more likely to get warns taken away by the staff who issued them that are still staff because they're actually around to give their opinion.
Warns are a permanent record, they're more than just slaps on the wrist if you amass enough. If your behavior becomes better than you won't be warned anymore and it will be okay.
If it's just to get a clean record, people will know you are a good player if you are a good player, regardless of your past warns. A clean record doesn't really matter that much.