I saw the ifixit guide, OWC PDF, and a video I stopped watching half way through.
At this time I'm not comfortable doing the upgrades myself, and since this is a pretty steep purchase for me don't want to Bork it. I will try an upgrade down the road when these machines are less expensive.
Same spec machine sold for a little over $300 from the same buyer. I was outbid and away from computer / internet at the time.
Since the seller is pretty quick to response to messages, I feel good about buying from him. Is flexible on different drive arrangements, and even will let me use my drive. I have a 1TB spinner drive which is a little fat, need to research if it will fit in MM.