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

Yes, sorry it's a 8 3/4 swap. It had (has) a 8 1/4 in it now. Some people said that the driveshaft I have MAY just work... if used temporarily.
The stock 4" axles actually have green bearings (someone must have changed them at some point?) So these 4.5" axles should just slide in and go, huh? Well... and the brake conversion.

What about the gear oil? Is there a fill tube? How do you know how much to use?

Thanks!