Is my transmission "blown" ? on 1999 Ford Taurus

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Yesterday I brought my car to the mechanic to fix a squeaky belt. He said that it is not the belt, that the spring in the automatic belt tightener came out and that I need a new one. I paid $200 for the part plus labor. Today I was on my way to walmart and the car started revving and the RPM was going up and down. I drove to the shop instead, which is less than half a mile down the road, when I was trying to turn into the shop my car stopped moving completely. My boyfriend pushed the car to the side of the road, we went and got the man from the car shop and he filled it with transmission fluid and drove it the 100 feet to the shop. He said it was probably just a leak in the tubes. He put the car up on the lift, shined his flashlight in there, said there is a hole in my transmission pump and that my car is totaled unless I wanted to pay for a brandnew transmission plus "at least" $1200 in labor. Now mind you I brang my car home, which he sold me 6 quarts of transmission fluid because "that's what I would need to get home" and I didn't have to fill it once so that was also money wasted. I looked it up on the computer and the part they "fixed" on my car yesterday is attached to the piece that is broken today, it also says that you can replace a transmission pump and says nothing about having to replace the entire transmission. Sorry this is so long but I wanted to give all details. So, what should I do?
(1) Answer
I pulled out of a parking lot and went about fifty feet at about eighteen miles per hour, then the trany slipped. The next thing I know, the trans. no longer was engaged. It won't go forward but will go backwards. What do you think?