N.O.S. & Hypertech Question

I just got my N2O put in today and the guy that done it said he removed my whole tune because of the timing advance that the chip gives it. I understand that but, he told me that I could not use the programer to correct my speedo because if you use any feature on the programer it would mess with the timing. Is this true or can I put in my programer just to set my gears in so the speedo will be correct?

I just did that to fix my speedo. I don't think it will hurt it but the guy that installed it sweared it would.. of course I get home and after dark take my car out and 2 guages lights don't work and the oil psi goes to the max when I turn my head lights on. soooo..