<<<will I need a crossover cable, whatever a crossover cable is?>>>
No, a crossover cable is used to connect two computers directly - "Network Adapter to Network Adapter". When connecting to a hub/switch/router, straight-wired CAT5 patch cables are used.
<<<the best place to get some Cat. 5e cable online?>>>
Unless you need a substantial length of cable, you would be as well going to a local computer shop and buying a couple of cables, thus saving the exhorbitant "post & packing" costs of online purchasing.