Nothing needs to be done, just remove it, throw it in the bin and block up the rear oil gallery. Done.
Some interesting reading taken from another site:
Engine balance and deleting the balance shaft
With any engine balance is important, especially for high rpm operation. It’s a common misconception that the balance shaft is used to balance the engine. It is not. An engine’s rotating assembly is balanced so that when the crank is spinning in a circle the weight at any one point is the same. This makes it so that no uneven forces to try and move the engine in a particular direction at any point in it’s rotation. Hence the spinning is ‘in balance’. A great example is a tire. Have you ever had tire shake or driven a car before the wheels were balanced? Same thing. These forces at high rpm turn into a vibration which literally shakes your engine apart. In a motor, you add or remove weight from the crank, make sure the rods and pistons weigh the same. The 3800 uses external balancing as well, with a weighted balancer and a weight on the flex plate. The better the balance, the higher the rpm the engine will survive at.
Consider the math. An imbalance of one ounce (the weight of a rod bolt) 1” away from center at 2,000 rpm will be subjecting a force of 7 lbs. At 4,000 rpm, the force grows to 23.5 lbs! Double the speed again to 8,000 rpm and the force becomes 114 lbs! Keep in mind, this is one 1” away from the center of rotation. The idea is to show why balance issues are negligible at low rpm but insanely important at high rpm.
The 3800 has 6 cylinders, two banks of 3, 90 deg apart (90 deg V6 engine). This engine is actually 2 inline 3 cylinder engines together. At any given time a cylinder on the front is in the same position as a cylinder in the rear. The crank shaft has 30 deg offsets for journals where rods are next to each other. This 30 deg, plus the 90 degree V gives you 120 degrees. 3 cylinders x 120 degrees gives you 360 degrees or a full circle.
This design has some inherent problems though. As the 3 cylinders on one bank move up and down a shock is generated as they change direction (at the top and bottom of stroke). This shock cannot be countered by the other bank because they are on a 90 deg plane from each other. This creates an annoying harmonic that doesn’t affect engine balance or performance but it is noticeable in the car. As the engine speed rises, so does the frequency of this shock and it’s not felt much as it’s absorbed through the mounts and chassis. A good example of this is a subwoofer vs. a tweeter. Bass is low frequency sound and you can hear it for a long ways, it shakes your car. But no one ever complains about a neighboring cars mids or tweeters because higher frequencies do not travel as well or shake other objects. Same principal.
The balance shaft is an out of balance rod that create a harmonic to counter the feel of the inherent engine shake. The balance shaft is statically balanced so it will roll smooth but it is dynamically out of balance with weight on one end and an apposing weight 180 deg off on the other. This is done on purpose to cancel out the vibration inherent to a 90 deg V6 cylinder engine. Mainly it does it’s work at idle and low engine speeds where vibrations are felt the most. It does not keep your engine in balance; in fact it is purposely out of dynamic balance which is bad for performance. This trade off is worth it for the average consumer. The real problem comes when you want to use the engine at high engine speeds. Remember the math above about forces as they relate to rpm? It just so happens that the radius of a factory balance shaft is just over an inch but the out of balance (counter weight) is a lot more than an ounce! This translates to terrible internal engine shake and HP being used to create this vibration. For high rpm engine operation, it is recommended to eliminate or disable the factory balance shaft.