Subwoofer Magnet

I just bought a 12 inch kicker comp subwoofer off of eBay for a couple of bucks but the owner (resale shop) said they were unaware of what was wrong with it if anything. So I took the risk and bought it and when it got to me, I realized the magnet in the inside must’ve shifted and it doesn’t mechanically move or “boom” as it should..

It was making a grinding noise stopping it from working properly when pressing on the speaker up and down and then I push it up from the bottom and now it only goes up and won’t push down at all.

What should I do here?

Does anyone know a store or shop I could take it to for repair?

Is it something I could do myself?

I’m located in St. Louis