How difficult it is to change burrs? Can I order a unit without burrs?

Changing out the burrs will not require realignment, nor will it affect the alignment of the grinder, so no worries there. :) But the tolerance can be tight (between the burrs and carriers) so be sure to set aside some time to do it - other than that it should be pretty straight forward. 

If possible, we generally do prefer to have the burrs installed so we can do the complete QC (with burrs). However, if that'd be a hassle on your end, we can certainly accommodate that.