3DS Troubleshooting Assistance Needed

Hello, all, first post here so don't mind any weirdness detected. I have recently acquired a broken 3DS off of ebay with the hopes of fixing the thing, and sure enough, it is broken. I have it plugged into a working charger and the charging light does actually come on and the system appears to charge. After a bit when I turn it on, I do get a red light showing it's charged a tiny bit and unplugging the power cable, it does actually start to erratically flash red in a panicked means of telling me the battery is dying. However, this is just about all I can get out of the console. The screens won't turn on. Audio is dead. Headphone jack is dead. Can't tell if I'm using the camera or playing a game or if the system is just sitting there doing nothing. I do know I can hit the power button and then hit other random buttons and it'll shut off, so I'm under the assumption that for now, the system is actually running and I'm just having I/O issues. I have also noticed behind the battery port that there is a possibility for water damage judging by the little white and pink-splotched strip. I can't get the thing open for the life of me but if I do I'll send more information on the internals of the system.

My question, after this long-winded explanation, is... where do I go from here? I have not owned a 3DS before and I want to know how else to troubleshoot it so I can determine the root cause of the problem. Have I already identified the issue and just don't know it? Do I need to take certain other steps to identify the problem?