To replace the drive shaft's u-joints, begin by lifting up your car and securing it with pair of axle stands. Once that's done, you'll need to drain the transmission fluid, to ensure that it doesn't start leaking once we break the drive shaft apart. With that in mind, you can then remove the mounting bolts that hold the driveshaft to the gearbox. It could thus be dislodged fairly easily after you remove the driveshaft yoke. On the driveshaft itself, you'll then need to remove the bearings, bearing caps, and yoke, before removal of the u-joint can begin. Finally, repeat the process in reverse with the new u-joints.