Thanks for the info. guys.
When you say let them do the "filling and grinding", are you referring to just the very last amount of detail work to get the metal close enough for plating, or do you mean I should inquire as to whether they would fill and weld entirely the marker lamp holes I intend to get rid of?
Could I cut my metal to fill the holes, weld things up to the best of my ability, and then let them take over? And the same with installing the new lamps in another location. I feel confident that I could cut the holes, and weld in the necessary flanges and such needed to mount the new lights. It's the detailed finishing that concerns me when it comes to having a good surface for plating.