I have to agree with LarryBible.
You should change the fluid and filter and just drive it some more.
I have heard and experienced people trying to do this. Just because there is some "stuff" in your tranny does NOT mean you have to rebuilt it! If it dont drive, well thats differnt.
Change the fluid and filter and cross your fingers.
I had a tranny rebuilt, torque converter, and flex disk from MB dealership using MB parts, parts plus labor was $4000.00. 2 year/24,000 miles warrenty.
The reason why it went out so fast, well losts of reasons, lack of maintence (changing filter and fluid), driving the car when low on tranny fluid, towing or other "severe driving conditions", etc.