It's best to collect up as many manuals as you can, from different sources/authors and other years near yours. Then you can cross reference between them because some do contain a few errors. Yamaha didn't issue a full manual every year, only about every 3 to 5 years. In between model years just got a small supplement detailing any changes to that year. But sometimes you won't find all the changes if some occurred the year before, they would be in that previous year supplement. Perfect example in your case is the carbs. Your carb set was used on the '76-'77 models. There's no mention of it in the '77 supplement, details are in the '76 supplement.
So yes, you will want to download the full '75 service manual along with the '77D supplement. I would also download the '76C supplement as well ..... and the '78E manual Robin mentioned. Like I said, the more info you have, the better. There are also parts manual downloads available which can be very helpful. The exploded parts diagrams are a great aid when working on the bike.
As far as places to lube, I'd say anything that moves, lol. Off the top of my head, some of the important ones are the throttle cable, clutch cable, clutch & brake lever pivots, and the worm gear. Others include the footpeg, side, and centerstand pivots. Many of these basic, common sense lube points get sadly neglected on many bikes. I've found more than one worn out clutch lever, the pivot hole worn oval, because it was run dry all the time.