You should call the 401k provider and explain the situation. They will tell you whether you have enough in the account to be able to leave it there. If so, you can just chill until you come back and decide what to do with it. I have left money in prior company's 401ks for over a year before. It may not be a long-term solution, in my case after a year I got hit with fees and that prodded me to move it.

Moving it is actually quite simple: you open up a new Rollover IRA account (perhaps even with your current bank), and that bank gives you directions on how to tell your 401k provider how to send them the money directly. If it's sent directly, you won't have any tax implications for the transfer other than filing an additional form with this year's taxes.