Everyone has their own way off thinking on stuff like this.
If the trans pan has a drain plug, why not drop the pan and change out the filter? It's only a few bucks for a filter and new pan gasket. That filter will probably have a good amount of material in it from wearing in a brand new transmission. (I certainly wouldn't want to starve the trans of fluid because the filter was loaded with material). That's always true of a new/rebuilt engine. I always change oil/filter after the first 50 miles on a freshly rebuilt engine. Then, run 1000 miles before changing again. But, just my 2 cents worth.
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