I think you should glue it, but carefully with epoxy resin like Araldite, and try to do as good a a job as you can to cover the cracks. As long as you have the missing pieces of plastic it should work, but any that are gone for good, you can use some body filler maybe? Its worth trying to save if the motor still works as these are hard to come by nowadays, and you shouldn't be defeatist - you are a vacuum cleaner collector and you have to take the rough with the smooth - many a vac is gonna come to you in a bad way, look upon it as a challenge to put them right again.
Now chop chop lad, and get gluing lol