What is going on and how do I fix this?

First, what's leaking?

honestly I have no idea. I know so little about cars, but it does not look like oil

What color?

If it's dark like used oil, do a "wick test" (let a paper towel soak some up) if it has a red tint to it, its transmission....if its green or possibly orange (dont remember when they switched over) its most likely radiator coolant

Okay, I'll do that. If it is one of those things what should I do?

Also, I appreciate you taking the time to help me

Well, once you figure out what kind it is (also coolant will feel more watery as opposed to oily) the next step is to track down your leak and fix it

I mentioned the wick test because I'm suspicious of it being transmission fluid due to the description of how the temperature gauge acts between driving and idling

Thank you. Do you think the leak would cause my temperature to rise? And could the leak be caused by a routine oil change?

Depending on what the leak is yes its possible

Thank you for your help. My car has been treated. Just wanted to follow up and let you know, the cause of the temperature gauge spike and no heat was due to an air bubble in the tubing. The leaking was something completely different.

Glad to hear you got it fixed

If ur car runs hot check your thermostat or your fans could be a heating cord it is inside the dash hope that’s not the problem bc it is expensive