I've been having problems with my Murray lawnmower. It idles very low
and stalls frequently.

This problem started when the wheel broke on my lawnmower, so I had to
tilt the mower back to add a new bolt on it. Since i did that, all
kinds of fluids are inside parts that aren't supposed to have fluids.

I took off the part above the gas tank (sorry, I'm a computer geek,
not a lawnmower handy man, so I don't know the names of these parts)
and noticed that the greenish colored filter was soaked with a liquid
that smelled like gas and looked like oil. I squeezed it dry as much
as I could with a large rag and replaced it.
Then I removed the spark plug and noticed that there was oil in the
threads and the top of the plug was very black and looked burnt. I
wiped it clean as much as I could and replaced it.

Then I added new gas since I heard that last season's gas might be the
cause of the low idle problem.
I still have the problem of low idle and frequent stalls.

So basically my question is this: what else can I try and how do I
clean all the parts that're full of fluids that aren't supposed to be?

Thanks in advance!