Complete Assembly and Boot Guide: Pironman 5 with NVMe SSD fails to

The narrator in the ‘Complete Assembly and Boot Guide: Pironman 5 with NVMe SSD’ (https://youtu.be/tCKTgAeWIjc) hurriedly states that the first thing you must do (before visiting Rapsberry Pi’s site to dl the Imager) is update the Raspberry Pi 5’s bootloader by copying it to an SD card. That’s all he says. He doesn’t say where to find it. Presumably, it’s a location that is hosted somewhere by Raspberry Pi but not accessed via the Imager. Where do I find the latest bootloader for the Pi 5?

For information on how to install your system to an SD card, or SSD, please see our online tutorial:
https://docs.sunfounder.com/projects/pironman5/en/latest/install/install_raspberry_os.html

Thanks, but that’s the same video for which I shared the link. It gives conflicting information from what the written directions say to do. The main question I have is: Is it truly necessary for me to disassemble the whole thing or can I update the bootloader, install the OS, etc. NOW, without damaging any circuits, with the whole thing is already put together?

Yes, you have assembled the pironman5 case. You have assembled the pironman5 chassis, now you said you don’t know how to install the system to the SD card or SSD, and then connect the pironman5 to boot the system?
You don’t need to dismantle the case, just follow our tutorial to download and install the system and connect it to the pironman5 case.
What step are you currently stuck on, not how to install and boot the system?