Well, tank is back to almost full function. The new pump faceplate is on, and properly attached to the system. Viola! No geyser!
Now I'm wondering about my protein skimmer. When I plugged it in, it didn't fully fill for awhile. After 20 minutes or so, it filled so full that the upper cup was 1/2 full of water and the bubbles were overflowing. Is there an adjustment somewhere for the water level?