Hmm... I had GPU issues with 1809, but none with 1903. Try DDU first- make sure to set Windows Update not to automatically install drivers.. If that does not fix the problem, try this:
Check Windows Integrity: sfc /scannow
If all is good:
DISM /Online /Cleanup-Image /CheckHealth
Should be successful. If there is an error, hit me up.
If you still have issues, do an in-place upgrade. (Make USB media using Windows 10 Media Creation tool and run setup while in Windows).
Wi-FI driver should be as simple as downloading from manufacturer's website, disconnecting from internet, uninstalling using Device Manager - then - running uninstallation tool in the driver setup directory. Reboot, install manufacturer driver, reboot again, try to connect.
PS: 8gb RAM got screwed by the Spectre/Meltdown fixes. InSpectre by GRC used to work, but not with 1903. You will need Registry patch. Check steps here: https://support.microsoft.com/en-us/help/4072698/windows-server-speculative-execution-side-channel-vulnerabilities-prot
EDIT: Looks like GPU issue got solved? Now it's just Wi-Fi? If so, then disregard this post.