Ghostwall and ICMP rules

Hi,

recently, I decided to setup a Firewall on my notebook since I had to reinstall my OS (Win2k SP4). I liked to try out Ghostwall instead of buying a commercial heavy-weight Firewall containing features, that I believe not really neccesary for me. I am quite happy with this decision, and, being not very familiar with setting up a firewall, after some reading here and elsewhere, I think I managed defining a suitable ruleset. I do not have a private network and I am not behind router. But there are some questions remaining which concern ICMP and DHCP:
First, is it possible to define a ruleset for ICMP which takes the different types of ICMP traffic into account? And if this is not possible in Ghostwall itself, would it be reasonable to allow all ICMP traffic and to try defining "IP Security Policies" in Win2K like outlined here?

http://homepages.wmich.edu/~mchugha/w2kfirewall.htm
(Although I do not have any clue how to perform this.)

Second, when I connect to the internet (via 3Com PCI Ethernet) and I have got my IP from my ISP, I noticed some UDP traffic on ports 67-68 between my IP and 255.255.255.255. This was first blocked by my default rules, but now I decided to allow this. Why should I?

And finally: Do I need any rule that allows all traffic between my IP-Adress and 10.0.*.* on ports 67-68?

Could anybody give me some advice, please?