Q, I haven't seen a turntable recently either, and I think never with a pre-amp. My two certainly hadn't.
This Optimus is brand-new, from Dick Smith Electronics, which is the Australasian version of Radio Shack. About US$75.
Compressed air will take oily gunk off a motor. It would have to be something approaching glue to resist it when you get the nozzle up close. 110psi and considerable volume. The worry is that flying debris would add scratches, and I wouldn't want to do it on a turntable.
Neither would Cluin.