Go when the tire shop is LEAST busy, so they don't rush and screw up your wheels & tires.
Years ago I made the mistake of going to an ordinary Firestone tire shop to get mail-ordered M&H "DOT racing tires" installed. These had very floppy sidewalls, and the gorilla running the tire machine took a big chunk out of the tire's bead. Got into a big pissing contest with the manager to get reimbursed for the damaged tire.
I haven't seen M/T drag radials first hand, but I expect they're very soft. Review it with the manager ahead of time, so he puts his smartest/ best guy on your job ...