1997 Buick Skylark V6 3.1 Ltr
Transmission type starts with a 4...

So I replaced the radiator because coolant was getting into the transmission fluid. When I replaced the filter a light metal piece fell and I put it back in the only place that was obvious to me(I know).

Here is a drawing of the piece:

http://westpalmbeach.craigslist.org/com/594261578.html

I attached above and on one side of the filter, with the curved part pointing down. Looks like it keeps the filter from being pushed up. It slipped into two small projections above the filter. But later I did not recall seeing it last time I replaced the filter but could have just overlooked it.

Also now I am getting a transmission drip on the passenger side. And it only occurs after the engine is cooled way down. I have checked with the engine running and for a few hours after. Next morning several drips.
I got under there and could not tell, maybe an axle seal(?).

But the past few days I have also been getting a couple drops the tranny pan gasket. Which means coolant still leaking or too much pressure for some reason. Where else can coolant be leaking into transmission beside the radiator? Coolant color looks ok and the trannsmission drips and dipstick color looks ok(but they looked ok last time too). If coolant is getting into the transmission how come I have not had tranny liquid in the coolant?

Anyways I know this is one for the shop but I wanted to get an idea.
Thanks.