I also have a Nissen radiator, and had to drain it from the lower radiator hose connection. It did make a mess, but I had a 5 gallon bucket to catch most of it (make sure to remove splash pan if you have one). I recently bought a lower hose for about $13, so unless it needs replaced, you probably shouldn't cut any holes in it. Overall its a somewhat messy job, and I would recommend some new antifreeze and water, and once everything is back together and sealed, you should be set.