Yes, I would replace the clutch. I looked up the clutch at Seneca River Trading and see it there for $8.25, it is not a genuine Whirlpool part. The pads on those clutch bands wear out within just a few loads. That is probably what is producing the dust you are seeing. As far as the coupler, as long as none of the plastic fingers are broken and the holes in the rubber isolator are intact, I wouldn't worry about it. Before you put the gearcase back in, grab the brake cam driver and rotate it by hand CCW while pushing to make sure the basket drive and brakes are fully up into the brake hub. It should be fairly easy to rotate the basket drive this way. If it seems really tight make sure the brakes are releasing (not sticking). If they are releasing but it still seems tight, there may be clothing stuck between the tubs.