Dave, are you talking about the hydrostatic transmission filter or the main hydraulic filter? There has been lots of discussion lately about faulty filters failing for the hydrostatic transmission, but none about the main hydraulic filter failing. If yours is the hydro filter, your dealer should be able to get you the special high pressure filter for winter use.
How much did you overfill? A gallon or more? I don't think that would cause overpressure. It might cause leaks from somewhere else, but I think pressures in the system plumbing are regulated by pressure relief valves to limit overpressure.