Yep, those are the ones to watch. 197 & 198 are usually in sync and any non-zero value there usually causes picture breakup. They can usually be repaired with fix-disk though. A high number of reallocated sectors (attribute 5) can indicate a failing disk but the most important aspect is the rate at which the number is growing rather than the absolute value, although a high number will mean that the disk has to do more work.