I have a 2002 nissan altima that burns oil the light just came on a few days ago...
When I turned my engine two days ago I noticed smoke coming out of the muffler...
I read here that it could be the head gasket or other things... to be more specific when I check my oil it goes low and black what should I do? And do you know how much it will cost to fix?

1000-1800$??

If your oil light is on, stop; do not drive until you put oil in it. You will ruin engine. Cars burn oil from age, worn valves and piston rings. Just keep oil at proper level.

Let me rephrase I made a mistake on top... my ervice engine light went on this week and I got a oil change on Friday yesterday I checked the oil and it was low and awfully black. I started the engine a and smoke began to come out. Could it be the gasket?

OK, that's a lot different. Check engine light can mean a lot of things. They can also mean nothing. Oil smoke is blue, gasoline smoke is black. Burning oil is caused by worn rings, valves or valve guides. Blown head gasket will cause engine missing one or more cyclinders. Can cause hissing noise. Sometimes have mix of oil and water.