I'm done with my CCNA and taking the exam this September. The best software simulator you can have without buying equipment is Network Visualizer 4.0
CCNA1-deals mostly with the fundamental issue, network terminology and protocols, LANS,WANS, OSI/TCP model, network standard.
CCNA2-is really fun, this is when you get to configure the routers, learn about its IOS, routing protocol (Distance Vector),TCP/IP and access list.
CCNA3-slightly longer, most people think it's the hardest part. There is more configuration on the router and switches. IP addressing techique like VLSM, implementing routing protocol (RIPv2,OSPF,IGRP,EIGRP),VLAN,trunking,
CCNA4-easy. Mostly network terminology again. NAT and PAT,DHCP, PPP,ISDN,DDR,Frame Relay,network managment.