Thanks, it's indeed the pinion seal. This is definitely pushing the my pool of knowledge, especially when trying to speak intelligently.
IIRC, he said it's just the seal he'll replace while he's "down there". This was coming from their senior tech not a green tech. But I do agree. I try to avoid replacing things that aren't broken.
Re: the cap spinning, prying it up against the drive shaft held up camping over the weekend. I'm going to talk to them more as I still can't find that part by itself so I'm curious what's going to be replaced and how it will keep from falling down again.