yeah mate you just replace the whole plate cover its held on by the jet screw [the brass one in the middle] next to the bulb and the O ring around it and put the float back on you will see when you pull it apart
it should only cost around 10 dollars or so for the plate and O ring
any dramas let me know as im not very good at explaining things
Further more make sure you get a genuine plastic primer plate, the aftermarket ones I have had are not very good.
When removing the old cover watch for the little float and needle which may try and drop away, if the needle falls out you might have trouble finding it unless you are on a even surface like in the shed (Experience here lol)