All guides are from the Disney Infinity Modding Wiki, it has tons of great information.

-Basics of Modding Disney Infinity: (A great place to start for beginners)
 https://disneyinfinitymods.fandom.com/wiki/Modding_Basics

-General Modding Tutorials Tutorials for various things: https://disneyinfinitymods.fandom.com/wiki/Category:Tutorials

-Texture Modding and Swapping: 
 https://disneyinfinitymods.fandom.com/wiki/Texture_Swaps

-Modding Tools and Software: (A list of helpful tools) 
https://disneyinfinitymods.fandom.com/wiki/Modding_Tools

NOTE: FOR THE MOMMENT MODDING IS ONLY POSSIBLE ON DISNEY INFINITY GOLD EDITIONS WHICH CAN BE PURCHASED THROUGH STEAM