4.88 gears with 35"

Im think about putting 4.88 gears in my truck and i was wondering how hard would it be for me to do it myself? i really dont know a lot about gears but im willing to learn if it will save me a couple hundred bucks. Also i have read that if i want to put 4.88 gear in my truck i will have to put a new carrier in is that true or not? What kind of mpg would i get with 4.88 gears and 35's? I also have a rear locker is that going to make it hard for me to get gears for it?

 

Now if i would go with 4.56 gears would i half to go with a new carrier?

 

Yeah that's what my brother is doing with his taco...except since he has the ARB in the rear he is having YotaMasters install his 4.56's out back. As for the front he is buying a whole front carrier from east coast with an ARB/Gear combo, and we are going to slap it on ourselves!