X2 take photos, especially of the inside of the valve body showing the channels the check valve balls were in.
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The FSM should show those check ball locations, but pictures pictures pictures. There may be check balls of various sizes, so you'll want to make a note of which ones go where. Some of the screws may also different lengths, so I built a cardboard template and poked them through so I knew which screws went where.
We're probably scaring you off with all our warnings about taking pictures. Don't mind us, just do exactly what we say.