Converting to a manual will require plenty of work. You'd need a whole list of items including the pedal box, the transmission, the linkage, clutch cylinder, etc. It really isn't worth it unless you're willing to spend 2k+ on it. Labor will add far more to that.
Get a used automatic as they're pretty common transmissions.
E39 1998 BMW 528i Sport
E34 1989 BMW 535iM
E28 1988 BMW 528e
E24 1987 BMW L6