How do I clean my engine and give my Mercury a tune up?

I had someone pour chicken grease and bones into my water tank of my mercury. I had run it with the grease in there and I know it is atleast in my radiator prob. In my engine block. How would I go about getting this cleaned out. My car overheats within 10 of starting the car how would I correct this? I know it needs a new thermo. I can do this myself I am a novice car tech. (I can change my oil, and simple things of that nature) I can do anything as long as I have a starting off point. I also Know it needs a tune up how would I do this? I know these are alot of questions but I dont have anyone else that can do this or help me in this so any input would be invaluable. Thanks so much for your information