Yes, always dissemble and give them all the components.  That way they can sandblast and coat 100% of each component, where they side inside or each other.  I just got my Genesis 2000 back from Powder Coating last week, dozens of parts, and am in assembly mode now. 
I owned a manufacturing company for Jet SKI racing parts and have been doing powder coating since 1979.  Take a picture of all the parts, and list them so they will be added to the work order.  You can even give them all the hardware and they will blast in a strainer and hang on a wire to powder coat all the heads on your OEM or SS bolts.  I had my RC Planer Z-metals powder coated in the same batch.  
Hope to finish this weekend and will share my full restoration
They charge by the batch, not the part, so give them everything individually that does not get high-heat paint.
Enjoy your project.