Trying to change MaterialVariant properties using a script

Hey I am Max. I am working on a game that would require new terrain textures however my partner cannot receive photos because it costs money to send to where they live so I have to send a script through whatsapp.

I have been attempting to change the ColorMap, MetalnessMap, and NormalMap under a MaterialVariant in MaterialService using a script but I cannot figure out how to accomplish this. I am quite new to scripting so any help is very much appreciated.