1) IINM ~3liters. however thats based on generic proton gear boxes, may be different for BLM
2) should be at the GB oil sump
3) yes, and you will need a extended funnel, one with a long tube, as you typically can't fit the funnel at the GB opening
4) you need 2 person, 1 more to engage the gear while engine on etc, then check for it. there's also hot/cold levels where i am not versed at that yet. i typically leave it up to my mechanic