Swap current box for a 4k box

If I take my current box into the local Xfinity store to get a 4k box can Imjust walk in or do I need to make an advance arraignment?    

And is there a particular bus I should ask for?  I believe my current box is and XG1v3. 

I just ordered a new 4k OLED TV that should be delivered in a couple days.