I think that the hard drive on my KDS notebook is on its last legs. Are notebook hardrives basically the same, or are they model-specific?
They are mostly the same. There is a “standard” desktop size and a “standard” notebook size, and you can get adapters to fit notebook drives in desktops (but not the other way around because they won’t fit).
Laptop hard drives have gradually gotten shorter, and as they’ve done so, the drive bays that accomodate them have shrunk, so it’s at least hypothetically possible for you to buy a 2.5" laptop drive that’s too tall (too thick) for your computer’s bay. I doubt that your computer requires one shorter than 9mm though, and most of the drives you can buy in places other than eBay or SurplusDirect are going to be the newer shorter type. Putting a short drive in a bay that can accomodate a taller one, meanwhile, is not a problem. My PowerBook shipped with a 17mm drive and has a 9 in it now.
I thinke that this beastie is old enough that needing a new style anything won’t be a problem… 
Well if that’s the case be sure your MB BIOS can handle the capacity of the new drive. Most drives sold at retail these days are 20 gig minimum. Perfectly working smaller ones can usually be had on Ebay for cheap.
It has a 19 gig in it now.
When you remove your old drive (a pretty straightforward screwdriver procedure) you might find that it comes in a caddy, even if it is an internal drive. The only real purpose the caddy serves is to a) force you to buy from the OEM, and B) act as an adapter to the insides of the case. A lot of people mistake the caddy for the drive itself, and assume that a connector incompatibility makes replacement impossible
If you have a caddy, open open it up with, at most, a screwdriver and Exacto knife (be careful), remove the old drive, and save the plastic caddy for the new drive. Since you have your old drive, you’re golden. If you don’t have the old drive, you can probably get a dead/undersized drive+caddy for your model on eBay, fairly cheap.
Aside from the techie specs (e,g, what size your BIOS can fully accomodate), you should pay attention to the thickness of the drive (called “height” above). Typically, your laptop will accept either a 13mm or any size under 10mm. Obviously, a slimmer drive will fit in a caddy that will hold a thicker drive. Almost all modern drives are under 10mm, and will fit in older laptops – but it never hurts to measure your existing drive and check
What about power and data adapters? I’d be looking for a four-pin molex port for power and an 80-pin IDE cable for data, if I were moving a tiny drive into a big PC. Will tiny drives accomodate these connector types?