People often ask me if they can set up their own axle gears at home in the garage. It's possible but it does require a few fairly expensive specialty tools and a little bit of expertise in reading gear patterns. And, well, if you screw it up you can very easily wipe out your expensive new gearset and bearing kit. It's really not a good job for a first timer unless you have someone with you who has successfully swapped gears before.
It's also not really a job you can explain how to do in an email. But there are books about it. And one of the books that I would recommend if you are interested doing any axle work is Differentials Identification, Restoration & Repair by Jim Allen and Randy Lyman. There is a ton of info in this book that can help you identify what axles you have, how they work, how to regear them, and more. It's actually a pretty good book even for the experienced axle guy.