Pump started screeching - repair or replace?

[aquarium]

The pump is starting to screech and it sounds to me like a worn bearing, but being new to pools I don't know what a worn impeller or other moving part would sound like. It's a bit random whether it does it each time it starts, but I know where this is heading.

Is there any way to isolate whether it's a pump or motor bearing? It's probably quicker to just replace the whole thing for now and rebuild the old one later for a stand-by.

Here's a couple of pictures:





Can someone make a recommendation for a good replacement? It's a 1 HP.

Those short sections of black pipe are threaded into the pump, can I just use a threaded/slip PVC fitting there on the new one? Also, this would be a whole lot easier if they'd installed it with unions. Is there a reason why I would *not* want to install some new unions?

EDIT: Also, is it okay to use a PVC slide repair coupling like the one shown below on the suction side of the pump? That would make matching up pipe lengths a lot easier.