Hi nottstu, and welcome to AF
The answer to your questions is probably to install some apps.
Many 3rd party SMS apps support individual text alerts. The most popular are Go SMS and Handcent, though I'm currently using Pansi.
Separating text alerts from other notifications is more difficult (separating them from ringer volume or alarms is simpler). One way would be to set a silent tone as the default notification then something else for the texts, but it's a bit of a fiddle to change that. Maybe someone else will have a better idea?