I recommend making an appointment with your manager and asking if there are any options that would enable you to leave for a short period and then return without any loss of seniority, etc. You might get lucky -- and by talking with him/her directly, emphasizing that you like your current job and wish to return, etc. you will probably stay on good terms. Then, after hearing your options, you can make an informed decision. Whatever you finally decide, it should be put in writing (politely) so that it can be included in your personnel file. Of course you should give plenty of notice (at least 2 weeks, longer is better) and don't do anything nasty (such as leaving right before a holiday or calling is sick frequently to use up your sick time, etc). You want to make sure they have a good impression of you as you leave.
The hospital that I work for does not allow people to leave temporarily to take a travel assignment elsewhere. In fact, to discourage the development of a work force that "comes and goes" frequently, we don't allow people who leave to take a travel assignment to return to their old unit until they have been gone or at least a year. They may return to the hospital, but they must work on another unit. That may seem unfair, and it sometimes means we have to spend a few resources orienting them to another unit, but we feel there needs to be some "price to pay" for creating a hole in the schedule that needs to be filled -- and by having him/her work on another unit for a while (which shouldn't be too painful for a traveler), we end up with an employee who is more versatile.