I did this today on my 16ga and 18ga. The 18ga has 17,000 nails through it and is less than 3 months old. My 16ga has 139,000 nails though it in about 14 months of use. I have broken 2 drive blades and wore out the drive blade assembly once in that time and broke the PTO assembly as well. It is easy to work on after dealing with the junky ryobi nailers for a couple years. Take the plastic off and there are 2 bolts holding the back bumper on. The blade assembly falls out after that. If you truly have 100k nails through yours I suggest replacing the whole assembly because the part that the drive blade attaches to wears against the wheel and eventually prevents the gun from firing.