Can I get a ticket from Shanghai Hongquaio to Suzhou by train or bus when I arrive

Hello

I am arriving in Shanghai in a few days and intend to travel immediately to Suzhou by bus or train from the airport. I have not booked a ticket yet, will I have trouble getting a seat when I arrive at the airport? I am arriving Saturday afternoon at Shanghai Hongquaio and have a room in Suzhou that night. also if I book online from the USA can I pick up the ticket when I arrive? Many thanks