Could I fit the engine of a 2003 c/k 1500 into a 2000 chevy s10?
If I do, what else would I need to upgrade to make everything work together.
And will the after market parts of the s10 still fit on it? (Cold Air Intake, Headers, Exhaust, struts)

The answer is yes, but you never said what engine you have in your truck now or what engine you plan on putting into your truck.