A year ago, I had the input and output speed sensors replaced after the service light came on indicating a transmission problem. The transmission has always made a clunking sound and now it is having a hard time shifting from 1st to 2nd and 2nd to 3rd when doing city driving for a while. It jerks significantly when it finally shifts. It is usually fine in the morning on my 3 mile commute but if I am running around town or after coming off of the highway, it has a hard time shifting. The book states only to have the transmission fluid changed every 52,500 if you use the car to tow which I do not. Should I just give it up and get a new car as everyone I know is recommending? I love this car and otherwise it is in beautiful shape.
You need to have you problem diagnosed by a professional before you decide. Once you have a detailed description of what needs to be done (including problem codes), you can better decide. And you need an estimated cost to repair. Find a good, independent transmission shop to get the diagnosis. Ask everyone you know for a recommendation and click o the Mechanics Files button at the top of this page to find a good shop near you.
Has the tranny fluid been drained every 52k or even drained at all? Most on here recomend 30k, no matter wwhat. I would get it drained and the filter replaced. I just had mine done and it was only $88 at the dealer. It would be close to that buying the fluid, filter and gasket and doing it myself. If it helps it would be a cheap fix.
If the thing has never been serviced, then my off-hand guess is that it is toast. The hard shifting is probably because it is starting to slip. It won’t necessarily be enough for you to notice, but the computer would and would ramp up the line pressures to reduce slip - hence the hard shift.
However, transmissions are complicated things, you want to get a transmission specialist to diagnose as jtsanders mentioned. My guess is that you will be told that it is toast. In that case, if you like the car so much, price out the cost of a rebuilt unit with warranty. It will be a lot - but less than hitting the market for another car.