If you haven't accepted that payout yet, please, please have a look at what sickness insurance you have attached to your super. If it is up to date you may be much better off telling them to shove the payout, taking leave then sitting on your insurance--which is usually 75%of your wage--for a year or so until you are well enough to resume your normal duties.
Treatment can take a long time, I've got no income at the moment and was diagnosed 3weeks after I accepted a redundancy. I can't access my super insurance because of that and it will be nearly a year off work for me, then only going back part time. I'd have been nearly $30k better off on the insurance money than I was from the payout.
BTW, I'd love to get hold of your erroneous 'manager'. It makes me see all shades of red when I read things like that. They need edumacating, they do :)
Good luck @MKitty68. I don't want to complicate things for you, but that super insurance often gets forgotten. Marg xxx