Negotiating a new minivan advice

So my wife is in desperate need of a new minivan. She's sold on the new '18 Honda Odyssey, which literally is just making its appearance at the dealerships up here in New Hampshire. The conundrum we are in is that her current Odyssey needs a major engine repair but not worth the cost based on it being a '09 model and worth about the same price and the engine rebuild. Anyway, tried talking her into a new 17 or even another model but she's dead set on the 18 and can't blame her as she's hauling our kids around all day. Leads me to this question....given the van is just starting to hit dealers and they get one or two per delivery, it seems dealers won't be keen on significant savings off MSRP. Give me some good advice on how to approach the cost conversation? Do I just go straight to asking for dealer or factory invoice? I usually use USAA pricing (true car) but given its new true car pricing isn't even out yet.