It usually depends on a DC, its internal policies and all that. I’ve interacted both with DCs providing temporary access to racks on request so you could do stuff yourself, and DCs sending their own employees literally for anything, leaving you with zero access to the racks even if you are on site. In both cases I’ve never seen a scenario where making changes or maintenance is extra, on the contrary: I’ve seen tons of dudes walking with USB drives every single day for the favorite of mine “the user requested a custom iso boot” throughout the entire building.

Pretty much all you have to do is get to know their policy and that’s it.