If you want to run a full node, just run bitcoin-qt and forward port 8333 on your machine.
https://bitcointalk.org/index.php?topic=128122.0The CPU usage and RAM usage would be pretty low, but then you should notice a big jump in your bandwidth usage.

CPU usage is substantial on my laptop during synchronization and on incoming transactions. Of course it's an older model.
If you want to help the network the CPU should be able to validate transactions quickly enough.