Cisco Catalyst 3550 setup

We have a Cisco Catalyst 3550 switch with the following: 1. IP assigned & telnet working 2. internet access with dedicated ip (ethernet) 3. Local Networked pc's with manual configured 192.168.1.x range We need to configure the following: 1. proper routing for 192.168.1x range (belive its done using NAT) so the private ip range is able to reach the internet gateway as well as communicate in between (act as 1 network). 2. As we add more pc's to the network with manually configured private ip addresses, they should automatically be able to reach the internet 3. some hosts connected to the switch will have a dedicatepublic ip's assigned