Fender Jazz V Deluxe nut
 

I have played 6 string bass for 2 years now (15 on a 4 string) and I find myself liking the high C string but not using the low B that much. I'm wanting to buy a new fender jazz V and string it E to C. Question: Will I have to replace the nut when I do this? Thanks!

You dont have to but you should.
I would

Optimally yes, practically probably not. I use only brass nuts which would be a problem but with the plastic nuts that Fender uses it should be fine. If not, you are only out $10 for a new nut!