First time post-help!

2000 Caravan. 3.0 litre. 199,000 km.

Transmission oil/filter replaced (no flush) 1 week ago. Now it does not shift into gear properly, noisier and more sluggish. No problemsup to thispoint. Well maintained. Heard things such as "input/output sensor" replacement, etc.

What do you suggest?

 

What brand and designation of oil did you use?