general, i think you may have misread the article. to the best of my knowledge you can not run 100% cng in our engines because the diesel fuel also acts as a lubricant for the pumps and other moving parts, meaning without the diesel the engine would not be properly lubricated and break. as for the compressors, i have been told that if you have natural gas in your home then you can get a compressor for a decent price, but again i'm not 100% on that. i just looked on the internet for cng fill stations in my area.
the price of these kits that ya'll are looking at should come with a tank for the vehicle. i have seen kits minus tanks for as low as $650 on ebay and craigs list. if you are really interested in this then just look around and you can find them for a decent price.