I found my solution- thank you Jesse - the vid you send was helpful. If anyone has the problem I had, note that the new piece may be a bit too thick, so when all the gears are reinserted and you tighten the lid on top it will cause it to bind up. It works fine when you turn it by hand, but when installed it will not work correctly. Even though it appeared to be properly assembled when screwed down tight, the "lid" caused the entire assembly to bind. Jesse sent me a video show how to test it and how it worked when operating properly, and that helped me figure the whole thing out. As they say, a picture is worth 1000 words. In this case- it helped me figure out my problem! Thanks for your help... hope this helps anyone having the same problem!
Basically, by loosening the screw in the lid area over the replaced part it does not bind. I thought about trying to sand the whole piece, but instead installed tape over the crack so nothing will get in, and trunk is now working like a champ!
My part came in today. Took apart my trunk actuator, turns out it wasn't broken. I think the motor may just be getting very weak, it spins freely when I pull it out and power it separately, but just clicks feebly when engaged to the gears.