The floorplate broke off my Floormate H3000

I'm assuming that the floor plate your referring to is the wheel assy. This is a common problem on the H3000 series. You will have to remove the two pivot brngs on either side of the handle where it pivots on the base. Once removed, flip the machine over and you will have the necessary clearance to insall the new wheel assy. The difficult part will be attaching the front arm assy using little plastic pin provided. You can use a small pair of needle nose pliers to guide the pin into place and then use a larger pair of needle nose to squeeze GENTLY to push the pin into place. Once done, re-install the pivot brngs and your done.