Display coming away from back of screen assembly, still functional.

I would say most definitely you should try replacing the adhesive to repair your screen rather than trying to replace it, especially since it's still working. I give Dell kudos for supplying their service and maintenance manuals to the public, but sadly it doesn't go into quite the level of detail you would need; the closest it comes is in showing you how to remove the entire display assembly.

XPS 17 9700 Service Manual

Unfortunately, none of the screen replacement videos gives that kind of detail either. I'm not at all clear why no one seems to be inclined to replace the LCD without swapping out the entire display assembly, but you have a slight advantage in the fact that yours has already started self-disassembling.

Most of the time laptop LCD replacements don't require removing the display assembly from the main body of the laptop and I can't find any information on whether you'll be able to do that on yours or not. You might see how far you can get without taking it off; if something is hanging up your work you can always remove it at any time.

Just for completeness here's a video showing that process just in case you need it; hopefully you won't.

Fix or Upgrade Your LCD Screen Assembly - Dell XPS 17 9700 - YouTube

As you work, take lots of pictures so that when you're done you can use those to create your own iFixit guide to that repair for the benefit of those who come after you with the same issue. It's easy, fun and will earn the gratitude of the repair community.

Create a new Guide - iFixit