"The housing should be intact
"The housing should be intact with no cracks or warping, and should have nice shiny smooth inner surfaces.
The impeller should have no broken off blades, and when removed a rule of thumb is that if the blades nearly straighten out after an hour or so, it is not bad. If not it has taken a "set" and needs to be replaced. If it is older than 2 or 3 years it should be replaced anyway, as it is not expensive.
Most feel that if the drive leg is off or apart for any reason, change the pump impeller as a matter of course while you are at it.
Rod"