Uncorrectable is the main one to watch. That's the failed sector count. The Pending just means it had trouble reading and has scheduled a sector to be tested.
While disconcerting there are outside factors that can cause reading problems, loud noises, vibrations, power variations...
In any event, if you have everything backed up, if the drive fails you can be back up quickly simply by restoring the backup. I would make getting a backup drive the main priority unless you don't have important things you don't want to lose if the drive suddenly fails completely.