Generally very easy.
IF you want to stay with Windows, you can go to Microsoft and download a clean ISO for Windows 10 directly from them (assuming professional, not workstation) and then install that which gets rid of all the Dell stuff (you'll need to load drivers manually), so all you have is the Microsoft built in spyware and not any of the OEM BS.
IF you want to go with Linux and own your own OS and all that good freedom stuff, it's a matter of picking your distro, downloading the ISO and installing it.
if it's your first go at Linux, then I'd suggest this one:
Linux Mint 20.1 "Ulyssa" - Cinnamon (64-bit) - Linux Mint
If you like being a more rugged individualist and want to give the finger to IBM / Pottering, then go with:
Welcome to devuan.org | Devuan GNU+Linux Free Operating System
If you want to browse the endless distributions, go here:
DistroWatch.com: Put the fun back into computing. Use Linux, BSD.
Depending on which model (if you post the exact model, I can let you know), you may be able to add a second or 3rd drive to it & then run multiple Operating systems on it & choose which one you want to boot to.
You can also have Linux and Windows on the same drive with a boot menu, but that requires a re-install of both from scratch.