Replacing/delete the smk is not hard, I find hard to get the new smk playing.
Create a folder, add to the usual 5 txt. files a video.txt, write inside the name of the new smk, add the smk in the folder and create a wog file.

I did it in the past, however I was not able to make the new smk play.When opening game it brought me directly at menu, without anything playing. I guess the smk has to have a specific size and compression.