I just ordered a rebuilt 3.25:1 differential pumpkin to replace my 3.80:1 and bring my rpms down closer to stock and improve mpg (>8 mpg I hope). I figure I will drop from 3050 rpm at 65 mph to 2550 with 28" tires (roughly 800 rpm over stock). Everything I have read implies this is something anyone (even me) can do. So, my question is: Is it really this easy and what other parts do I need? Just a cover gasket?