Can someone recommend a good manual for converting ipchains to iptables?

Learn how to use IPTables so that you can convert it yourself.

www.tldp.org
www.linuxsecurity.org
www.google.com - if the above don't give the help you need

Agreed. Unlike converting from ipfwadm to ipchains there is no conversion utility. Your best bet is to learn iptables and by hand re-do your rulesets.

Iptables Homepage (http://www.iptables.org)

Iptables documentation (http://www.iptables.org/documentation/index.html)

It might be worth mentioning that there's a lot of similarities and if you are familiar with ipchains, iptables will not be at all different to get a good understanding of how it works.

Checkout some examples, after a hour you will be good with iptables!