go to autozone, pay $30 for 2 brute force heavy duty U-joints, and replace them yourself. all you need to do is drop the driveshaft, and use a vice or c-clamp to push the old U-joints out, put the new ones in (they're pregreased w. synthetic lithium grease) and then put the driveshaft back on. just make sure you mark the orientation of the driveshaft to the rearend, or you'll screw up the balancing and get vibrations. it took me only about 3 hours and ive never dropped a driveshaft before. if you want some more help or insight just ask...
oh, and I would only buy the aluminum driveshaft if I somehow broke my old one, because the stock driveshaft really isnt all that heavy (25lbs, tops)