I've actually replaced three Honda radiators that cracked from the top of the aluminum / plastic case. A site i recommend is www.radiatorbarn.com . For $125 shipped, you can get a all metal heavy duty radiator. As for a diy? here's a great one that i used to do my jobs, this is for the manual gsr.

http://www.team-integra.net/sections...?ArticleID=520