[Jakobud]

I have some PS/2 to USB connectors I was trying to use with a USB keyboard and mouse but obviously I can't tell if it's working without being able to see anything.

Those adapters did not work for me on my O2 so get an ps2 mouse and keyboard, a vga-able screen (or an adapter dvi, hdmi, whatever) and if necessary boot the installation tools and overlays cd 1 (archive.org) and set a new password if you cannot login or use the demos or guest login.
You should be able to open SoftwareManager (swmgr) as non-root too, just to see what's installed there.

Other possibilities are to use telnet (after an ipscan) or a terminal 9800/8/N/1

it is not so complicated - if you have some questions ask here

Okay so I could get ahold of a serial cable, and connect it between the console serial port (#1) and serial port on another PC and then use Putty or something to connect to the O2? Do I need some sort of login or something to do connect to it (like SSH or telnet)? Because I have no clue what the login would be. I just know the O2 appears to boot up to where the IRIX boot up jingle sounds and then light turns green, which I assume means it's a successful bootup. Do I just use a regular RS-232 cable? Does it need to be a null modem cable or is that the same thing? Been many years since I messed with serial cables.