Classic 50 Lower Unit Seal and impeller replacement

[paddlincwolfe]

My first outboard...... Mercury Classic 50 1989.
Milky oil in lower unit. I have dropped the lower unit and purchased a new impeller and seal kit.
I have search Youtube and watched most applicable videos but still could use some help.
I prefer articles over videos but either would work. Recommended article about seal and impeller replacement?

I am kind of stuck right not trying to remove the gear housing nut with the "splines" that look like it fit a special tool to match the "square teeth". I figure there must be a way without the tool. One video I watched suggested that this nut was vinyl or plastic but mine seems to be cast aluminum. I have tried gently tapping the teeth with a blunt flat round bar but to no avail. I am soaking in penetrating oil now.
1) Tips on how to remove this nut would be greatly appreciated.
2) Any articles, pdfs or videos on the lower units seal replacement would also be greatly appreciated. We have a boat access only cabin and I need to get up there this week so I could really use some help.
Sincere anticipatory thanks.
Cwolfe

 

[racerone]

Is there a special Lock washer in there with a locking tab that needs to be bent out of the way.

 

[paddlincwolfe]

Yes there is... and I bent the tabs back flat. I am afraid to apply much more force using the blunt tip bar out of fear of cracking/fracturing the nut.
Would heat help?