Definitely do not remove the deck plate. It is a casting which has a flat base bolted to the deck and a vertical socket (i.e. at right angles to the base) which fits inside the mast to stop the mast foot moving sideways. The mast fits over this socket but is otherwise just resting on the base plate.
Buying a replacement sailtrack stop is the best option but make sure you get the right size. When you unscrew the locating screw from the mast, the stop should be able to move freely down the mast groove to below the opening for the luff slides. There is no need to remove it (and risk losing it). It's worth noting that when relocating the stop by screwing it into the mast, make sure you screw it in far enough to the point where there is no thread on the screw so that it can be wiggled about. This prevents corrosion between the screw and the mast which may otherwise seize it. To unscrew it you will then have to pull the screw outward whilst turning it to catch the thread again. A bit of grease on the thread helps.