2001 Pontiac Grand Prix SE review from North America

Transmission fluid leaking all over the place.

Car usually starts jerking when it slows down to about second gear speed that, especially when the car warms up, that is, there is an Engine (or transmission) jerking after shifting when the car is hot.

I have a 2001 Pontiac Grand prix 3.1 Liter.

I took it to a lubrication place to change the oil and filter, and then they suggested me to do a Automatic transmission Fluid change (with pan), which I accepted.

Now about 3 weeks after the Automatic transmission Fluid change my car first started showing a "change oil" lights on, and now it is leaking pretty, pretty bad transmission oil all over the place.

I took the car back to the lubrication place and they say they don't know what's happening because all they did as change the Automatic transmission Fluid and that they are not mechanics and suggested me to take the care to a mechanic as soon as possible.

So I took the car to a GM service right away (because it was the only mechanic nearby), and the GM guys said they would have to first take out the transmission pan to check it (will cost $200,00).

After taking the transmission pan out GM says now that something is spilling the fluid all over the place, something is forcing the fluid out of the transmission.

But to see what is doing that, they say they will have to take the whole transmission down to see what's wrong, and they think it might be transmission failure.

So what should I do? I am a girl and know nothing about cars.

Could this transmission problem be caused by the stupid people in the lubrication place?

Could they have damaged my transmission by only changing the transmission fluid?

If so then they should pay to fix it right?

How can I charge then for that?

Before the Automatic transmission Fluid change the car never had any leak at all.

But I did noticed for quite sometime now, that my car usually starts jerking when it slows down to about second gear speed that, especially when the car warms up, that is, there is an Engine (or transmission) jerking after shifting when the car is hot.

Thanks in advance, please help as soon as possible, because my car is there and I don't know what to do.