$1,200 for new seems a little suspicious (significantly lower than what I paid ~18 months ago). But if is legit, my vote is buying the new unit is a no-brainer. One thing to check is whether the new unit is NOS, or more specifically whether it has the new internals for ULSD; if not, just stock up on lubricant.
I had a rebuilt from a reputable shop go bad in under 5K miles, so am now alergic to them.