Yes cpu is standard. Chipset is z370. Z390 chipset is backward compatible with 370.

work involves figuring out Dell LED controller connector (LED_CONTROLLER) pinout for power switch.  R8 is figured out, but not sure for R9.  For the time being you can remove the entire Dell power switch and move it to new case w Mb.

also you will lose IO shield as OEM one is not removable from case.

yw.

To avoid the IO failure warning on every boot you also need to remove the front panel USB connectors and bring them over to the new case and lose your USB 3.0 headers, or figure out which PINS require jumpers.

It's a standard processor correct? It would work in any Z390? I have 9700. I MAY swap it out for a 9900k. What would I have to do to get the oem mb to work with a new case? Thanks for taking your time to help me. 

Re: I am going to get a new motherboard. Can I salvage the power supply? Is there anything else that I need to change besides the MB?

if just OEM case is cramped, that does not warrant a Mb change.  Moving Dell proprietary board to new case needs some work though.

if you get a new Mb, it is a not a case change any more but new system build.

you can use Dell OEM psu, memory, video card, and even cpu if new motherboard is compatible.