Hi Ken,
I am not sure if there is anyway in 3.2.5, out of the box, to search classified ads (but I don't believe there is.)
I have integrated htDig with OpenACS 3.2.5, and you can use that to search classified ads. You can find more details about that by searching this bboard, and also by visiting http://www.theashergroup.com/sdm/one-package-release?release_id=3&package_id=1.