IIRC, you will have to drill a hole through the MSH to capture the spring and ball while you install the latch. It is very unusual for that spring to ever need replacing and the housing is not really made to be taken apart.
That is definitely a job where you need three hands and a good vise. Be very careful to keep your face away from the direction the spring will shoot if you lose control of it. I have done it without drilling a hole and pinning it in place but I wouldn't want to do it again. I'll bet you won't either.
