I actually had more vibration problems with my modern drive shaft and went back to the original.
The originals are a bit like CV joints: As long as you keep the dirt out they'll last a long time. And as long as the housing hasn't gotten worn where the balls move back and forth, then they are pretty cheap to repair. Used to be, and I think it is still true, that you can get the rollers, balls, etc. as a separate much cheaper service kit. But as long as they are kept lubricated with clean grease, that will not be needed very often.
Yes, there should be a cover over the end. And there is supposed to be a spring between the end of the driveshaft and the cover to keep the shaft generally centered between the transmission and rear axle.
I've had better luck with the leather boots than with the rubber boots. I think most of the rubber boots are old stock ready to fail, but the leather, especially if slightly greasy or oily, seem to last forever if properly installed.
PS: You don't need to remove the pin if all you are doing is cleaning out the old grease and re-lubricating them.