i also have a seris d rb
best 5x4 camera i own, lots of fun
perfectly weighted and easy to work on
if you need to retime the shutter on your own.

i would ask the owner of the shop to give you a "demonstration"
of the shutter, so if there is a problem it is on his dime ..
sometimes the metal edges on the slots get bent and jammed up
so the shutter doesn't wind ...
if the shutter was stored wound up, there might be some issues too
with the master spring being stretched. but that is easy to deal with
when you retime the mechanism ...

have fun !