loud knocking sound and now car wont turn over...what do I check first?

Hello haleysmith10cb2623, The questions you are asking has multiple answers. It should go without saying that attempting to answer this question without first performing at least some minor inspections requires quite a bit of guess work. You have mentioned a high failure item on the VR6 motor which is the timing chain. The timing chain on this engine is located on the back of the engine and requires the transmission to be removed to get access to those components. If this vehicle were to be at our shop the first thing we would want to do is check whether or not there are any timing "correlation" diagnostic trouble codes in the computer. This would allow us to know if there may be additional damage to the engine and how to proceed from there. Please let us know if you have any additional questions. Thanks, Joe -Elite AutoCare, Inc. Eliteautocareeverett.com