It will run, but it will definitely be smoother if your system had more RAM. RAM is relatively inexpensive, as bluedoggiant has pointed out, and is a great way to boost your Macs performance.
Do it!Do it! I got 2G of OWC RAM for under $50 too. It's Hynix memory, the same as the stuff in the MacBook. So no worries. Your computer with thank you. Leopard will thank you.