SOLVED!
Big development! I took the computer apart again, pulled the CMOS battery, reconnected only the monitor and touchpad and keyboard, and plugged in the AC charger. I also had tried to plug in a USB drive with the BIOS download from Dell on it, but I am POSITIVE is wasn't read by the computer. I powered on the laptop and got a black screen and a 2 beep error. A quick google search told me that a 2 beep error corresponds to RAM (?). I powered off the computer and installed my memory cards on the motherboard. I started it up again and got a black screen and a 5 beep error with I think corresponds to CMOS. I powered off, and installed the CMOS battery, and turned it back on. I think I got another beeping error, but this time I pressed the ESC key (not sure if once or repeatedly) and the dell logo flashed, some white text showed up on the screen saying "checking media.......failed checking media". Then a prompt to press any key to reboot came up. I rebooted and then spammed F2 or F12. I did run the pre-soimething assessment even though I knew most of the components weren't even connected. I connected the rest of the componenets and powered it on. I got into the BIOS with the other key, and had read a thing about how to go to the boot settings and find "Windows Boot Manager". At first, the option wasn't there, but I did "load optimal defaults" and restart a time or two. Eventually somehow "Windows Boot Manager" did show up under the UEFI boot tab. I used F5 and F6 to move it to the top of the list, since it was on the bottom. then I saved and exited. My computer actually booted right up to the dell screen with the little spinny wheel, then my log-in screen came up! I was so happy!