4 speed ka-booom !

You cannot convert a ball detent cover to a rooster comb cover if that's what you are thinking. But if your ball-detent levers have stripped threads or well rounded corners from running loose, well those are hard to repair.
The reverse lever is cover specific, so if yours is not too badly damaged, I would not change it.I would, however renew the O-ring on it.
I use any light grease to hold the needles. Vaseline is too light at room temp, but works if it's cooled.
As to the C/S, they have 4 lives; this way,that way, upsidedown way, repeat,lol. I'm running a 1968 model.
Personally, I'd buy 2 sets of brass rings. On account of it doesn't take much of a tweak to get them out-of-round, which makes them more or less junk. I have saved them but it takes a special touch.You may end up not needing to open the second pack, but ..................better to have the option, than wait for another pack to arrive. And you'll need em sooner or later. It's a normal wear part.