It is always a pleasure to reply to those who do me the honor of reading my articles!
SMART information should appear in your Disk Utility when you select the drive itself, towards the bottom of the window (if memory serves me well, I no longer run a Panther machine). Alternatively, you can use an application such as SMARTReporter to perform checks for you.
Do note that a drive can fail without its SMART checks detecting anything so be on the lookout for strange noises, increased whirring, clicking or "write noises." Detecting drive failures is an inexact science so always keep good backups. On the upside, a damaged drive is rather unlikely to cause slowdowns over a long period of time – it would indicate the drive is moribund.
My first recommendation would be to check for background processes that would eat memory or resources. Open the Console utility and check the Console and System logs for spurious logs (some applications get so busy logging errors they hog the hard drives). Open Activity Monitor and check for high memory or processor usage.
I hope this helps!