Boom rubbing on gooseneck

[afterwork]

Hi all.

Checking my rig this weekend on my Jeanneau Sun Odyssey 50 DS and I found that the gooseneck is getting worn down by metal to metal rubbing from the gooseneck to the boom (see attachment). I am guessing I am missing a nylon washer to avoid the metal to metal rubbing. I have a couple of questions on this:

1. Can I just add any nylon washer to this or do I need it from a specific material to be purchased by the gooseneck OEM?
2. What is the best process to lift the boom to add the washer? Do I need to fully remove the sail? Do I just tie the halyard around it to give it a lift while I remove the bolt?

Apologize in advance for such a noob question but want to make sure I do this lift right as the boom is very heavy and dangerous if mishandled.