I have a custom, chrome oil tank on a 2006 FLSTNI and want to change the oil myself. Do I disconnect the rubber tube connecting the oil tank to the lines going into the case since there is no drain plug or do I syphon the old oil out? Furthermore, another rider told me that if I drain the oil in the crank case that simply filling the tank with oil won´t replace the oil in the crank case and I would need some kind of machine to refill it. Is that true?