York compressor

Been thinking about getting rid of my nitrogen and buy the york set up or just trying to build it from scratch? I know i can get the compressor from autozone , but what about the oiler and the water/oil seperator and other misc stuff i need . Or should i just go ahead and fork over the 699.00 that they want for it . Oh ya guys that already have one do you have a back up 12 volt for just in case it breaks or do you trust it? Basically is it worth it?