About to start rear end swap... a few questions?

I have never attempted this before, so if someone could give me some input it would be great!
I still have the stock slant 6 leaf springs on my car, so I bought some XHD Mancni Springs to swap with the rear end. Should this be a pretty simple swap over?
Also... I bought new 4.5" axles, when I swap those over that should just be a simple swap too, right? I shouldn't have to do any adjusting with the gears, would I?
Now for the really stupid question... Where do I put in the rear end oil? Is there a filler tube on the rear end itself?

Thanks much!!