Ok, I know this by heart. Atleast I think so...
SPOILER! SPOILER!
When you find the Raider Base there is a safe there. It's trapped and you need 3 Dog Tags, one from each of the Raider leaders. The tags are named from the chars in the movie The Good, The Bad and The Ugly. Once you have the tags in your inventory click on the safe and you should be able to open it. Take the stuff from it. If I remember right, there should be a notebook in there. That would be the "logbook" of the Raiders.
The best way to break in to the Bishop Family's safes is to get the briefcase from Thomas Moore at Vault City. Then shag the dames and raid the safes in each of their rooms. Mr. Bishop's safe however is trapped. Then just walk in to the room where Bishop and his men are. Then talk and agree whatever you wish to agree on.
If you agree to assasinate Mr. Westin at NCR then just travel to the NCR. Talk to the sheriff/police chief at the corner of the store INSIDE the city walls and ask him if there are any work avaiable in the NCR. Then go to Mr. Westin's ranch gate and talk to the guard and say that the sheriff sent you. There is also a drunkard at the "barn" near by. Bring some booze and talk to him and he'll tell you his story. Then go to the house's door where Mr. Westin is and talk to the foreman. He'll let you in. And now you have two options, well three actually. Shoot him, poison him or reveal everything to him. Shooting him is for Duke Nukem 3D fans (slaughter everyone), poisonin him is for Hitman 47 (use poison syringe and steal the nitro's from the doc's place) fans and telling the truth to him is for Lawful Good (just tell the truth) chars.
After telling the truth I wouldn't go anywhere nearby Bishop''s Casino.
Allthouh (is this spelled with two L's or not??) no one at the NCR will officially say that they hired Mr. Bishop and his croonies to persuade Vault City to join the NCR.
Read all dialogues very carefully and all holotapes you get. Just figure this puzzle out and you will find it actually very simple.
/SPOILER / SPOILER