2002 Dodge Caravan transmission problems

I have a 2002 Dodge Caravan SE 3.3L 6 cyl. with 97,200 mileage. The van was brought to an Oil Express on August 4, 2012 for an oil change and transmission pan service (not a flush). After driving the van home I noticed the transmission jumped when breaking. Please note the van was driving fine before bringing it to Oil Express and has never displayed any type of transmission problems. I drove the van back to Oil Express and the technician told me that this was not uncommon after having a transmission pan service. I should simply drive the van for awhile and it should clear itself up. After driving the van for a week the problem worsened. The transmission would jump while driving at a constant speed. I brought the van to a Dodge dealership and the mechanic told me the seal had let go and the transmission would need to dropped, overhauled and the pump replaced. The mechanic felt that Oil Express had done nothing wrong and that it was simply coincidental that the problem appeared after the transmission pan service.

I am definitely not a mechanic but concerns that I have are:

If the seal had “let go” wouldn’t there have been some type of transmission leakage beforehand and wouldn’t the check engine light had gone on? The van has never leaked transmission fluid and the check engine light did not go on.

How quickly can a seal simply let go without displaying any signs of trouble?

Can a seal be seen with the visible eye if the transmission has not been dropped?

Can a pump be seen with the visible eye if the transmission has not been dropped?

Is it worth paying over $2,500.00 to repair this van and will it continue to have transmission problems even after the overhaul?

Thank you.