If I were you I would change the fluid and filter to make sure the filter is clean and make sure that the fluid level is correct. Purchase a can of Sea Foam trans additive and add it to the new fluid. This should clean up the inside of the transmission and make it shift better. One word of caution, don't let anyone talk you into a transmission flush, as they are bad news on high mileage transmissions and don't believe what the tranny shop told you. If they were that aggressive they just want your money.