Level of difficulty changing 8 3/4 gearing
You need a dial indicator, micrometer, press, torque wrench, a inch pound torque meter and a face spanner wrench.
If you have all of that then you have the tools to attempt it, if not it would be in your best interest to have someone qualified do it
OR, the good point on drop out centers is you buy another with the ratio you want and just swap them. . . .