so, my car was sent to the shop to change a new head gasket just a few days ago. my car is an old 2e toyota engine which I was thinking of painting it to look nice. But in order to paint it I have to open the cylinder head cover, which was just sealed up by my foreman. I'm not sure if i have to replace the head gasket again or clean and reapply a new RTV sealant
No, you cannot re-use that gasket, they are designed to crush as part of forming a new seal. So if you take it apart you will need a new gasket.
I think you mean "valve cover gasket", not head gasket. If it is of cork variety (of this I doubt, I would not reuse it. However, it is most likely a polymer flexible gasket that can be reused if cleaned carefully.
There is no reason to remove the head (and head gasket) to repaint an engine.