The shims in the upper arm control both caster and camber; if your "expert" cant get to the two bolts, I'd suggest finding someone else to do the job :) They're not difficult to access if a jack is put under the crossmember and the car is raised a little. They can then be reached using a standard socket (a universal joint between socket and extension might make it a bit easier).

Some recommend that caster be adjusted by shimming the crossmember so that it tilts rather than using the upper arm - the unequal thickness of shims needed between the front and rear bolts of the arm to set caster angles can produce a twisting force on the bolts and the arm, leading to possible fatigue and breakage of the bolts. I've never tried this method so can't verify its worth.