We agreed that it was worthwhile experience.
We talked about the concert being worthwhile.

Please don't apologize. I'm here to help you :) This is absolutely right. After "talk about" we can't put another clause like "that is was worth while". It needs to be a noun.

I talked about postponing school by one year, but my parents thought that was a bads decision.
My sister talked to me about her summer vacation.

http://grammar.ccc.commnet.edu/grammar/verblist.htm
This website gives a list of which verbs are followed by gerunds (doing, being, working, talking) and which are followed by infintives (to do, to be, to say)