I'm hoping someone on here can provide some insight as to what I might do next and whether or not I've damaged my car in more way than one.
To give you some insight as to what happened, my AC isn't working. It flashes when pressed and then turns off, the compressor doesn't even turn on. I've already tried recharging it with an AC PRO Recharge kit with no luck so a mechanically inclined friend of mine helped me out and scanned my car with a Bluetooth dongle like thing (Blue something or another was its name) and there came up being no codes... which was unfortunate and left me (per his advice) with only the option of pulling all the fuses and hoping one of them was blown. (I tried looking at the diagram for the fuse layout in the driver's side dashboard fuse box, however, it is only useful for the trunk fusebox and the driver's side fuse box, not the engine bay. And also seems to be fitted for an older Mercedes based on the diagrams within it. So my friend and I pulled each fuse individually looking for anything, corrosion, a blown fuse, nothing. All the fuses are in working order (We didn't test them, but visually they appeared fine).
The important part of this all is that in front of the driver's side fuse box, there is a large brown grounding wire that goes from the fuse box to the body via a screw and nut. We pulled that off and noticed some corrosion and cleaned it best we could (the car was off at this point and was throughout pulling all the fuses, no lights were on and the key was not in the ignition, we did not, however, remove the negative battery terminal.) Upon screwing the wire back to the frame via the nut and bolt it rests sandwiched between, we decided to clean the outside of the car but had some difficulty maneuvering the sunroof, the motion can best be described as jerky and unresponsive to many of the movements of the sunroof switch, only moving 50-60% of the time we tried to push the switch. We eventually got it closed, but haven't touched it since.
At that time we were confused but figured since we had had problems with the car's sunroof in the past it was simply the car being an old car. The next problems came after we had finished cleaning it and were about to drive off, we turned the car on and our dashboard lit up like a Christmas tree, with ABS and ESP lights and the circular screen in the center telling us there were faults in the ABS and ESP systems, and to visit a workshop. We were quite startled to find these lights as we didn't touch anything in those two systems except the fuses.
In addition to these lights, power steering seems to be a bit funny and requires more than the usual amount of effort to turn.
Since then, we have let the car sit overnight and drove it briefly this morning only to find that the check engine light is now also on.
We are planning on taking the car to an AutoZone/Advanced Autoparts store to get the car scanned and see if any of the codes were because of "low battery voltages" or something of that nature since we did disconnect that rather thick and seemingly important grounding connection and did re-socket/check every single fuse in the car. I've done what little research I can and it seems the low voltage could bring on those lights. We won't fully know until later today.
What I'd like to ask is for any advice or help of any kind. I'm a fledgling of a mechanic if even that and this was the first time I've really gone fiddling with my car.
If you could help me get a handle for what I may have to do next and whether or not my car is actually broken in any of these ways I would be most appreciative.
Thank you for any replies!