Using Google is pretty easy.
Just type this in the search box.
For the RCR sub-forum:
site:gt40s.com/forum/rcr-forum-rcr40-slc-p4-mkiv/ "search term"
For the clubhouse:
site:gt40s.com/forum/slc-clubhouse/ "search term"
Make sure there is a space between the url and your search term. This also comes in handy when doing national craigslist searches etc.
For example:
site:craigslist.org 2g eclipse for sale