This is a very easy repair. Pop the cap off the top of the wash plate with a screwdriver, then use a socket to remove the bolt. Remove and replace the wash plate and bolt, tighten it down and re-insert the top cap.
IMPORTANT: Use a new bolt for this repair, or if re-using the old bolt, apply some medium-strength thread compound before installing. Otherwise the bolt loosens after a few washes. (The replacement bolt comes with thread compound on it already.)