If you go with a tummy tucker skid plate, you will definitly need an sye and cv shaft. I would go with the Carolina combo for $350. You can't beat that, anywhere. As for the skid plate, I don't know. I would also recommend adjustable control arms for the upper and lower. The uppers are important because they will allow you to adjust your pinion angle in the rear, and your castor angle in the front. The lowers will keep your axles centered and leave them at stock wheelbase. I would not recommend putting in the belly up, even with the sye and cv shaft, without being able to adjust your pinion angle. A belly up can give you from 1" to 3" of clearance, and that equals out to some extreme driveshaft angles. Also, if you keep the belly up, but go with a bigger lift in the future, you will probably need a super short shaft sye to compensate for the increased angle. If you buy a bigger lift in the future, I would use the belly skid that comes with the kit to keep your driveshaft angle more managable.
I know from personal experience that harsh driveline angles, if left unchecked, will lead to very premature driveshaft failure.