Here is a copy of the report given by Infiniti technicians:
"Found many codes in ECM. Cleared and most went away. Found engine sludged and appears to have been cleaned. No further work/diagnosis performed at this time. Note vehicle is leaking badly from valve covers, oil pan, rear main seal, steering rack, power steering pump and brake master cylinder and red brake light is on. May also have other leaks but will need to repair known leaks and thoroughly clean under vehicle to check for further leaks...Vehicle is in very poor shape."
The car did have an oil change right before it was purchased, but it's unknown how long it went before then without getting one. At Autozone, someone was nice enough to get up and look under the hood and they saw that the fluids / oils were still fine, which baffles the hell out of me, seeing as that was the day that the car ended up dying.
Also, Infiniti technically never was able to determine whether or not the car did have any electrical problems (although one of the advisors she spoke to over the phone suggested that maybe a sensor was faulty) because they apparently stopped the diagnosis process as soon as they discovered the sludge and the leaks.
It's funny you say that, Q451990, because I have a 1992 Lexus LS400 that ran great at first and then had a series of electrical problems (such as constant episodes where literally every single power operated feature in the car, including the seats, would die) that suddenly disappeared one day, and the car began running as normal with no issue whatsoever. The car was fine for about three months when it ended up dying in the middle of a parking lot; it appeared as if the transmission was fried this time, but I had the car towed home and the very next time I tried to crank the car, the "battery" was totally drained.
Back to Infiniti talk, the service technician was nice enough to talk to my mother over the phone. I listened into the conversation and he seemed to think that the car was just a bad car. He also said something about the sludge problem causing intermittent misfire, which I'm somewhat skeptical of, seeing as the car evidently has a long-standing history of sludge, yet in 3k miles of being driven (and that car has gotten the hell driven out of it), it never misfired until days ago. Anyway, my mother is thinking that the electrical problem that the car could have is perhaps the oxygen sensor.