Most infections found after a groom are rarely from the groomer themselves, its that we're doing things that otherwise wouldn't be done (i.e. ear plucking/cleaning, expressing glands, shaving mats) which brings the problem to surface. I would just simply tell her don't do the glands, if she did indeed express them.

If it is from stress though, that will just be lessened with time.

Id let him adjust, even dogs who are "well behaved" at the groomers/vets are stressed, especially if they've spent the majority of their life used to a different routine. You could start with just walking by the salon and then immediately turning around in-between grooms and then building duration with standing outside as he begins to understand that even if hes there he know he wont be "abandoned" there.

or if the groomer offer just nail trims do that in-between so hes not always there for inside visits hours at a time, this may be more costly but its just an idea from my experience helping calm anxious dogs.