The expansion valve is relatively easy to access, but there is one caveat. The bottom pipe retaining nuts (two) aren't too bad, but don't "horse" the upper ones or you'll flex the pipes and have an evaporator leak that you didn't have before where the pipes join the evaporator (weld).
The Golden Rule
1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)