Easy? No. It can be replaced without removing the intake manifold, but it's not "easy." I would use a long 1/4" drive extension and a 12MM universal socket to break the bolt loose, accessing from the driver's side of the engine bay. Once you work the bolt out of the threads, You can pull the sensor and bolt together through with the harness. Reverse to install.
Get yourself a multi meter and get on utube and type in checking knock sensor on your car. they do go bad but with small hands an a lot of cuts (the gaskets are stainless steel and will cut you) they can be replaced without taking the intake manifold off the engine($600.00).
Otherwise have the fuel pressure checked. On these older cars the fuel pump can trigger the knock sensor code. I have a 1996 infinity with 268000 miles and it runs fine but does have problems with vacuum leaks which can cause a lot of problems. misfiling, poor gas mileage, pcv valve codes. Diagnosis in 1996 was in it infancy and OBT2 codes were also. The problem is often far from what it says.
I have also had to take the intake manifold off to replace the valve cover gasket. A common problem. I have had the transmission fluid replaced every 75000 miles. (synthetic)