First thing we did was remove all the shelving units from its previous life as a service van. Then we had to drill out all the flooring rivets, which was not easy. We scrubbed the interior and started researching insulation. (Basically Heather's second full-time job for weeks. It wasn't pleasant.) Once insulation was decided on, we put down sound-proofing and insulation on the floor, painted the floor boards, and re-riveted them in place. (Heather nearly lost an eye. Wear safety goggles, people!) Then it was on to the walls - Reflectix, mineral wool, and the factory walls back in place (because we didn't know any better and it seemed a good way to save some money). We prettied up the one big wall that would be exposed with a geologic map that we happened to have laying around. We found some cheap wallpaper-ish covered plywood (with matching slats) that was perfect for the ceiling. More Reflectix, foam board insulation, and then we screwed the slats right into the ribs across the ceiling to hold the panels up. (Note: finishing washers make everything look better.) Then we got a great price on one sheet of walnut veneer plywood and used it to replace the gray plastic panels on the doors. It was nice to have a perfect template for cutting those out (again installed with sound-proofing, Reflectix, and mineral wool underneath)*. And with the surfaces basically done, we were ready to get started on some serious electrical work...
* (Not included in this write-up is the utter nightmare that we experienced with rivet-nuts. On multiple projects. We're sure it was somehow user error, but we will never recommend those evil things to anyone, ever.)