The creature replacement is done by replacing two lines in the characteristics file - character visual and map object (I can't write more precisely without a computer)
Copy these lines from the wizard's characteristics and paste them into the wizard's characteristics, then find the map object and monk in the data.pak file and copy the bottom line, like CHARACTER PRIEST, and paste it into the corresponding wizard file

Or you can rewrite the path to the wizard's file from CharacterVizual/free city to CharacterVizual/haven
And rename the files inside the folder so that the game recognizes them as monk files, do the same with the map objects, the last point of the first method also needs to be done