Changing position within present company

Hi
I have been offered a position in another department in the company I currently work for.They are putting alot of pressure on me to take it.

I have to go in & sort it out - set it up & put systems & people in place.
I have said I am interested if ,once this is done that I take over managing this department along with the two I currently manage.

I don't know how long this would take but I think maybe 9 months.

I want to know if taking this job in the other department affects my current contract - in that is it like starting out in a new job- or does continuity of service still apply even though its a different job?

Thanks

Are they offering you a new or altered contract?
I would have assumed that your service would remain unbroken.
Maybe the DETE Employment Rights Section can apprise you of your statutory rights in this context?