Lincoln/Mercury Repair: Transmission, worst case scenario, metal shavings

Question
I failed to mention the mileage in my first question its 120k and although the transmission service was performed a few weeks ago the car has only been driven about 200 miles since then.I figure my worst case scenario would mean that I need a rebuilt transmission if thats the case what should I expect to have to pay for that service on this vehicle.Also do you have any recommendations for service ...a transmission shop or the dealer ? Thanks Again.

Followup To

Question -
I bought a 2000 Mercury Sable on a private sale for my son yesterday and last night was looking at the maintenance receipts the seller had given me.What I found was that the car was in the shop twice within the last month for "Transmission not shifting out of 1st manually".The mechanics comments the first visit to the shop were"transmission shifted perfectly and there were no codes stored in computer".The owner told the mechanic it happened 3 months ago also but went away then as well.The mechanic recommended updating the transmission range sensor for possible cause.They replaced the Range Sensor.The second trip to the shop was to a transmission specialist about 2 weeks later.They evaluated the vehicle and findings were "speedometer not reading when vehicle moving and erratic speed sensor signal on scan tool display.Transmission pan dented and excessive metal fragments on the magnet.Transmission has beginning stages of an  internal failure".The work performed here was to replace failed speed sensor and service transmission although it stated the owner opted for this service meaning that there was another recommendation.So now I am left wondering if I just bought a car that needs a transmission in the near future.I would like your your opinion based on what you have read as to how extensive you think the problem might be.

Answer -
Sables are nice cars, I bought one for my son also. Dented pan is impact, so the guy that had it before hit something in the road I would guess. But metal shavings are a natural phenomenon found in the manufacturing process of transmissions that end up on the magnet or in the filter. Speed sensors are common, nothing to worry about there. The thing that bothers me the most was that the transmission was serviced. This could end up causing a problem, but then you could get lucky. I didn't see the milage on this but you need to be carefully over 70,000 miles with this model of transmission. Never, ever change transmission fluid. Nope, never! I think that if it was going to fail due to the service, it would have probably done it by now. Usually, servicing will cause the transmission to crash anywhere from 2 weeks to 2 months after it was done.

Answer
Hi Tom,

I am not impressed with dealers in anyway. If you need to have your transmission overhauled it's best to stay with someone that specializes. Independent shops are ok, usually a little less expensive, but lack the training and don't have access to important information such as upgrading and modifing transmission components to make sure this won't happen again. I suggest a Cottman or an Aamco because they are large, nation wide chains. 866-COTTMAN for one near you or 888-GOAAMCO I think for Aamco. Of course, if you live near Las Vegas... I would be happy to help!