Spider gasket

How can I know for sure if that's the problem..?
I've owned a twelve year old in ground cement pool for eleven years but I don't attempt repairs often. I can't get my filter to draw water. A pool owner friend did some over the phone diagnostics with me and she says it's either the spider gasket or the multiport spring. I just popped the top off of the multiport but honestly, the spider gasket doesn't look bad at all and neither does the complete top part of the valve. I'm not sure how to proceed. She feels it's either the gasket or the spring, as water comes out of my backwash hose in varying degrees when the valve is on any function. (very small trickle when it's on 'filter') Pool was opened the week before Memorial Day this year and ran fine but trouble started a week ago Friday when my pool opener returned to vacuum.
 
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