Remove the fill plug first.People have drained the old oil, and not been
able to open up the fill plug. I always wondered what they did then? Put
antiseize compound on the plugs before reinstalling them.

Some people have used a 17mm bolt to open up the drain and  fill
plugs.Spin a nut or two on the bolt and tighten them  up against each
other . Jam nuts.Then stick the bolt head into the fill plug and use a
wrench loosen. Fill plug first!!