If its a MH or HPS just clean it up and put in a new bulb. I don't think there's much toxic stuff in there, compared to a fluorescent or mercury vapor lamp. If its a fluorescent of some type, there's a chance for mercury contamination. But you should understand that there's actually very little mercury in the tube (a couple dozen milligrams), and if there's great ventilation then don't sweat it and just replace and keep going. Of course there may be hazards locked up in MH and HPS bulbs that might poison you or your crop, so I'll let others chime in.
