Agreed, if the filter was advertised as new and you got a used one... a refund, return, or exchange is in order.
The filter should be ok. If you put brand new media in, all that's really left is all of the plastic parts + the motor. You can clean that stuff easily.
You'll need bio, mechanical, and chemical media.
Generally speaking, the bio media you rinse monthly.
The mechanical media ... Sponges you clean and reuse. If you're using filter floss... you just replace it.
Chemical - carbon needs to be replaced monthly or Purigen can be cleaned and re-used.
For the filter itself... Make sure the impeller is clean and free of gunk. If the motor starts getting loud, the impeller is usually dirty.
There will be a rubber o-ring between the two canister pieces. Lubricate that o-ring with vaseline from time to time so it doesn't dry out. If it dries out the filter could leak.
This might help...
viewtopic.php?f=9&t=30145