Nope. The anti-rattle cones don't normally help, and I've seen the pusher actually melt, and cause issues. It's a dumb band-aid. If seadoo didn't want their pumps to rattle... they should have used loaded bearings.
Yes... any synthetic GL5 75w-90 will work in the pump. Personally, I use wal-mart brand. A quart is only around $8. Mobil is going to be $20. Regardless... you only use 3oz so a quart will last a long time.