Hi Chefiam1, generaly I would strip down the cylinder heads, remove the rocker assembly, valve springs and valves. I would clean the heads of all the crap and deliver them to the machine shop in their barest form, along with the new valves, guides and seats if you have them. Engineers/machinists charge for their time the more you can do for yourself the less it will cost you.
The other advantage of this approach is that you can clean and check the rocker assemblies and etc while waiting for the machinist to do his job.
Bob