Do yourself a HUGE favor. REMOVE your oil pan to clean out all of the old oil SLUDGE. Even if you can get the old oil to drain, how will you ever be certain that all of the old sludge is gone? It sounds like you bought a cheap machine instead of a good one. A muck quicker way to check for sludge is to remove the valve / rocker cover. Chances are very high that if there is sludge in the lower portion of the engine, then there will be some sitting under the valve cover. If you put fresh oil that engine (without) cleaning out the oil pan) it will almost certainly kill that engine by interfering with the oil circulation through the engine. It sucks, but remove the engine, pull the valve cover & oil pan. Then clean the SNOT out of those areas until they are 100% clean. Be sure you blow a lot of air through the oil drain holes that are in the head. (Don't be afraid to use "too much" brake cleaner to get it all cleaned out. The key here is to restore all ports & oil drain holes to an open path for the oil to return to the bottom of the engine for recirculation. Anything inside that prevents free oil flow will only cause EXPENSIVE problems.) Then just reassemble. It is the only way to save that engine if it is SO "sludged" up that it will not drain. I've seen this on several engines that were neglected for many years.