[MBZ] A/C dryer replacement

[archer]

I need to replace a leaking pressure switch on top of the dryer in an '83 
300D Turbo.  In American cars the dryer is usually replaced any time a part 
in the A/C system is replaced, but I don't want to replace this $180 dryer 
until vacuuming and gassing up the system to see if this is the only leak.

All opinions on the pros and cons of replacing the pressure switch "without" 
replacing the dryer are welcome.

Thanks,
Gerry Archer
'83 300D and 240D