Beijing is closer to Harbin, you can get there by train. Well, Wuhan and Nanjing is in Southern China, where you should go by air from Harbin, or you may spend 27 hours on the way by train. Beijing has bullet train to Harbin, 8 hours are enough. Or you may go to Nanjing and Wuhan first from Beijing and then Harbin. The Ice festival is held from Early Jan, to end of Feb. There are three venues last year and the ticket fare is different, 100, 120, 150RMB. Not clear how will they hold the festival this year yet.