The WSS cannot be cleaned or anything. It either works or doesn't. I could imagine dirt getting in there, but with the tolerance between the WSS and the rings it'* unlikely. The WSS frequently go bad, and yes you need a whole new hub to get a new sensor. I worked for days trying to extract the old sensor in a spare hub, trust me, it'* not going to happen. If you really want your ABS, go to the jyard and get a new hub and put it in. It'll either work or it won't, if it doesn't work, hopefully your yard will replace it [mine does]. Otherwise you will be spending an arm and a leg + the cost of a new car to fix a primitive ABS system. I have ABS in my foot and I can what I would call shiver my leg for ABS. Works fine for me... but i'm a frugal little ****.
'89 SSE - GX3 -190k, 155k on body - Back for another ride.