I agree with majority, may as well service the ATF. Owners manual specs Matic D, which was some time ago, the same time frame as Dex III. Lots of choices for ATF now including synthetic based fluids that don't shear like the mineral based. 'If the vehicle was mine', I'd use MaxLife Full Syn MV ATF. Readily available and value priced at WM. Others mentioned previously also options.
So whether ATF d&fs over some period of time or trans cooler line exchange, servicing ATF a good call imo.