The vibration could be a driveline vibe, do you have a lift? if so how much? Usually with a 4" susp. lift the stock driveline will not suffice, A SYE kit and a CV driveshaft are the common answers.
U-joints are easy to swap and pretty cheap, if you're sitting stock I'd start there and replace them.
A little bit of play in the driveline especially at the drive shaft is normal, its the backlash of your gears in the diff.