You have the right idea, but screwed up your math <insert obligatory rant about today's youth here>.
5 V * 0.05% = 2.5 mV
Edit: Regarding the DAC, if you check the datasheet you see a severe lack of information for non-audio applications. This is one of the reasons that makes using such a DAC hard in non-audio applications. Can you, at first glance, figure out if that DAC works down to 0 Hz, aka DC? And what do you do with the bipolar output? Adding an offset? That requires yet another good reference voltage. Or do you know how the DAC behaves during its 1 min warmup period?
HP certainly knows more about that DAC then we know. Maybe Analog told them, or they measured it. Will Analog tell you, too, or do you want to run some test series to figure out the DAC? of course, if you like that DAC, go ahead, get a few, start measuring and designing.