What problems exist with removing the navigation bar during the checkout process?

I am working on a application that allows users to buy games. There is a sidebar with the global navigation throughout the whole app.

And I am now wondering if I can hide the sidebar during the checkout process. I started thinking about this for two reasons:

1) To let users focus on the payment process and not distract them with irrelevant information (like the navigation at that point) - like is sometimes done with registration process

2) I would like to show the summary of the shopping cart during the checkout, kind of display two columns at the same time and I feel like there's not a lot of space for all those elements to breath

This is what it looks like right now:

So I figured maybe I could hide that sidebar altogether to gain some space, but I am not sure if it's an entirely good idea.