Is it easy to install the rear end gears ive gt 3.42/

Depends on who you are and whether you have the tools. For some of us it's a piece of cake; for some others of us it's doabel but a struggle; and for yet others it's impossible to do it and get it right.

I would have to say that this is one of those things that falls into the category of "If you have to ask, you shouldn't try it". If you really want to learn how, find somebody that has done a few successfully, and pay them to show you how while they do it. THen maybe you'll be ready to do the next set.