Should I replace the pressure cylinder inside my transmission (170,000 miles) on 2004 Buick Park Avenue

My transmission is shifting hard after it heats up. The "presure cylinder in side the transmission may be acting up and needs replacement" is what one mechanic said and quoted me a $500 repair. It doesn't always shift hard and most of the time it shifts normally. this has been a problem since I bought the car in 2004. The light went on this summer that indicated a problem, but when they shut it off, it did not come back on. Since I have over 170,000 miles on this transmission, I wonder if I should fix it for $500 or just drive it until it gets worse and the light comes on again?

Will fixing it help my transmission to last longer, or with that much mileage, will I need to replace anyway in the near future and waste the 500 expense?
Thank you!

Scott Maline

Asked by for the 2004 Buick Park Avenue
been around 4o years and have never heard of a pressure cylinder. you need to take it to a trans shop and let them give you a real diag with terms that make sense. more than likely you will need an overhaul with the mileage.