Lots of BOS - PEK flights available....go ahead and book that and take a domestic ticket off CTrip. I just used it for the first time recently and it wasn't bad at all. I booked my tickets a couple of weeks prior to travel as that seemed to be the cheapest time. If you can afford it, skip the train - the prices for the flights aren't that much more, and it's extremely easy for a non-Chinese person....the train is also possible, but it much longer, and might be a bit daunting for someone inexperienced with China. Harbin's a great city - go for it!