Particles in the oil is pretty normal, as long as you can't feel the fragments if you roll the oil between your finger and thumb!
I'd take the car for a run, get everything up to correct temp, then drain the gearbox oil overnight, so it empties as much as possible.
The Comma oil? that you have, in my opinion would be fine, but check that you have enough of it to complete the job.
Check the oil again after a thousand or so miles, to see what the fragment situation is....
Welcome to the Forum btw

Thom