Stock chain length for your K3 is 100 links. The prices you listed are pretty reasonable, except for the rear sprocket. Z1 has the JT 48t rear for $35. Of course you have to figure in shipping, but they only charge postage. It's good to support local shops, but of course it's also good to support good online parts suppliers, especially when the owner is a long-time sohc4 forum member.
As for the front sprocket size, if you want your bike to have quicker off-the-line acceleration and don't mind higher rpm at top speed, then you may want to try the 17 tooth, but if you're happy with the current set-up, then stick with the 18 tooth. Z1 has both the 17 and 18 tooth.