It is simple to do and straightforward. Plus, it is cheap and you are unlimited in pictures of descriptions.
But, to post in the For Sale section you do need to be a contributing member and that can cost as little as $20. You need to go here: http://www.gt40s.com/ubbthreads/mypaymentpal/mypaymentpal.php?Cat=0 and become a supporting/donating member. Then, you will be able to post threads on the Car For Sale section.