A wobble is not usually a driveshaft issue. Driveshafts will often have a vibration on acceleration. You could slip under the truck and inspect the u-joints. Try moving the driveshaft with your hands, and be sure to chalk your wheels before you get under the truck. Either tires or warped rims usually cause wobble. I recommend having the wheels and tires inspected first; it will probably cost you $50 to have them balanced and examined.