Ive heard of people adding a drop of CA to those type of gears on some servos to add some strength to that bond.

I was going to try that next time one of my servos needs a gear set and I put in new gears that don't have any grease on them.

But yeah other than that replacing gear sets are easy for any one to do, just be careful and make sure everything is aligned. Shouldn't be a big deal.