42K miles does seem a little premature for the u-joints to be going out. Block/chock the tires and put it in neutral. Rotate the driveshaft and check for play in the u-joints (also check for the squeaking sound you mentioned). If they look good, then grease them up. If not, you can remove the driveshaft and try the various hammering, clamping and vise-grip methods to remove the bad u-joint. I find it easier to just take the driveshaft to a driveshaft shop, pay them $15, and let them have fun removing it. FWIW, Autozone has replacement "Brute Force" u-joints for about $13. Also, if one of your double cardan u-joints is bad, a driveshaft shop should be able to fix that, even though the manual says they're not rebuildable.

Hope this helps.