If the multiport valve body itself is not cracked then it doesn't need to be replaced. If the valve body is trashed then you have nothing to lose by trying to fix it. If the body is cracked at the threads I'd try JB Weld. Home depot, Lowes etc. I'd get a new PVC male fitting and smear it with the JB and thread it in and let it set. If the body is cracked beyond the threads then try the JB from the inside. the stuff is tough. As I said....nothing to lose. We're trying to see if we can see the pics you sent. I'm not sure how to do that yet. Maybe Ben is the only one who has access.
Al
Al