When no layered copy is left, an image layer separator is the fastest way back to an editable file. LayerGrab finds each element, puts it on its own transparent layer in its original position, and paints in the background behind it, so moving or deleting an element never leaves a hole.
Export the result as a layered PSD to keep working in Photoshop, or separate only the element you need to change.
Check the result before you build on it. Look at the edges of each element at 100%, compare the repainted background with the original wherever something used to cover it, and rename anything the model named too generically. Keep the flat original in the same folder: if a client later finds the source document, its live text and effects win, and the rebuilt version becomes a record of what changed.