Trust my ADSL modem/router?

[earni]

My firewall box has a hardware failure. So I decided to connect my home LAN directly to the modem/router. This begs the question wether it is worthwhile to run a separate box with an iptables firewall. After all the router provides NAT and port forwarding. So my internal computers are hidden and ports are not accessible from the external network unless I forward one.
I do not know wether it protects against IP address spoofing and there may be other dangers I am ignorant off.
I would like to hear what the readers of the forum think about this.

[dkeav]

well technically you will never be secure, though in reality your just as secure as everyone else

unless you are ebay or something in disguise, most likely you are not a very inviting target and only need to worry about script kiddies which good security practices like NAT and the use of a router can curb