Love RPGs, best of luck on your project! 
I believe there are inventory systems currently pending for the asset store, that may be useful for your game. Text tutorials I haven’t come across a lot.
For your particular problem of managing a grid. The way to do it right now is to store 2D grids as 1D grids. So what I do for my grid for turn based tactical games is, I created a struct that represents all tile data. Then I make a 1D array of size Width x Height. Then, when manipulating the grid, I convert 2D coordinates to 1D array index using this Macro:
So that is one piece of the puzzle in grid manipulation. Feel free to post more questions, I know there are people working on similar stuff. You can also PM me with any questions, I like tackling this kind of stuff (turn based and grids).