Question: oil leak

I have 2000 z28 with 200,000 miles on it.The engine runs good and uses only the oil that is leaking. It does not burn any oil. I have had a problem with oil leak. Had the rear seal fixed because the Chevy dealer told me thats where it was coming from. Still leaking oil and now they said it was the oil pressure sensor. So they pulled manifold to get to oil pressure sensor and found the oil pressure sensor wasnt leaking and they said it was the pcv hose that goes around to the back of the engine or some type of hose was deterated and leaking so theyre going to fix it. Also I am going to get them to change oil sensor while manifold is off and wiring harness for knock sensors because where hose was leaking it corroded the knock sensor harness's. Do I need to replace knock sensors or do I leave them in because I not throwing any codes on it. Is there anything else I need to have them to do while they have the manifold off.