is there any way to be able to have the script so people can place ads without have to go through all the register an account stuff?
How is this logical - if they don't put their contact details in how does a visitor contact them? You can make the registration pretty short. You don't have to ask for realms of information. What I can also tell you is if you don't have a registration process and you redeveloped a chunk of the 68C software to let people post without registering, two things will happen. Firstly you will get poor quality ads with no contact information and secondly you will get spammed continually.
