I always considered ICS a good exercise for masochists.

If you don't mind spending a little money, you might find a LinkSys WET54GS might solve your problem more easily:

http://www.pricegrabber.com/search_...&search=wet54gs

or if you don't need 4 ports and 802.11g capability, the cheaper WET11

http://www.pricegrabber.com/search_...word=wet11&rd=1