No experience with the Care/Care Plus plan myself, but the answers lie in the documentation in which they offer the plan and in your own legwork. Even if some of us chose the plan a couple of years ago, things can change. Their docs will tell you who will honor the plan and what you may have to do at your "home" dealer (if anything).
As for selling the plans at a "reasonable" price, I see three components to this:
- What does the service through 30K and 50K miles cost without the plan? Call a couple of service departments you'd be willing to use and ask. Also check your maintenance schedule and make sure that the major service isn't at, say, 60K miles (in which case what is the additional $400 buying?);
- Do you want your dealer doing the service? It's not required. I'm not a huge car DIYer but there are some very good local shops not far from me that can do all but the most specialized tasks at a better price and sometimes with more knowledge than the dealer's service staff.
- This is one of those "extended warranty" things, which typically are highly negotiable. After you've read the docs, call another dealer and see if they'll better the price. If you're good at negotiating, you can tell any dealer you're interested but don't want to put that kind of money into it -- and listen to what they say. As with any negotiation, you have to be ready to walk away.
Good luck.