Best way to transition to night shift?

Your plan seems more or less what I do; since it's a fairly late starting night shift, you could theoretically (depending perhaps on commute times) go to bed at a relatively normal time, get up very early in the morning, then take an extended nap in the afternoon. I know a lot of people at my work do that, so they can do stuff in the day still (although equally, a lot of them take naps on the nights anyway...).

I'd recommend sticking to your plan for the first one, and see how well it works, although ideally try and sleep as late as possible into the afternoon. It's harder to sleep in the day though, so you may well end up waking up in the middle at some point - that's fine, just try and get back to sleep again (don't feel like you need to stay awake once you get up). Usually my sleep while on nights is a bit interrupted and fragmented. Also bringing in some caffeinated drink(s) (e.g. coffee, tea, soda-type soft drinks) would probably be a good idea, as this helps you stay up (especially if you didn't sleep as well as you would've hoped in the day).

For going back to the days, it's usually just a case of forcing yourself to get up around noon-1ish, spending the afternoon/early evening in zombie mode, then going to sleep sometime after 6-7pm. You'll probably sleep through then, and be able to get up on time the next day. The day going from nights to days (whether you're working the days or off and just want to adjust your sleep pattern) is almost always a write-off, so don't plan to get anything done that day.