How do I make a Storage (Backpack) in a block that I can access?

So I am new to scripting and only know the real basic's, And the game im trying to create is very script reliant.

I have made the block I want to add the backpack in but how would I go about adding a script and a GUI to the block that I can then press a button when im within a few blocks range to access what is in the block? And how would I make it save?

Thanks in advance!

What your thinking of doing would require far more scripts than you think it would, for this I would suggest contacting someone who offers their services as a scripter.