however, because the worker opened the attachment in Google Sheets, all the formulas have been lost,

export to .csv from goggle version. Import to slave sheets in your version. clever formulae in a separate sheet referencing the .csv sheets. Export any ancilliary results in .csv format. Upload to Goggle version. That way your formulae are withinin your control.

Some if not most can be macro'ed.

Record macro is the way to go. Then tinker.

There are more ways of skinning a cat than choking it with cream and butter.