Just got a cheap car and noticed the water in it was nasty looking and the oil was looking a bit old. Drove car and temperature rose but never went to red. After changing the thermostat and driving down the road it went dead. Got it home and checked oil levels and it has water in it now. I was wondering if something I did while changing thermostat could have caused this?
When you replaced the thermostat did you run your finger around the coolant area to verify any sludge, metal, or contaminants? Helpful intake video: GM 3100,3400 Thermostat Replacement. I would also make sure you didn't accidentally disable something.
Per memory the Chevy Lumina uses the 3.1 that is known for intake leaks. I would suggest looking to see if you see any wetness around the intake. Since you've indicated the the coolant was nasty you might want to do a coolant flush, run for a little bit, do not drive and look at the coolant again.
There is a video on youtube that talks about the 3.1 engine: "3.1 GM Intake Manifold Gasket auto repairs done right 216-510-4583"
Also, whenever you open the coolant system you should make sure to bleed it and that wasn't mentioned in your question.