There is a third party ecommerce shopping cart - SunShop that seems to meet my needs. It claims that it is easy to integrate into any website.

What approach should I use to integrate into XOOPS? Module, Block or what?

Would this be a big effort?

Thanks in advance

I would use php includes in the appropriate files through out the shopping cart script. In many cases this will work for 3rd party scripts, but it takes a considerable amount of effort and debugging to get it fit right. The only thing you really need to worry about is conflicting CSS styles with div tags that are similar and such.

Once it's working, use iMenu to have custom menus on the side of your site to take people there.

This is how I would go about doing it, approaches and opinions will vary depending on the skill and patience of the developer.

Thanks.

Without a doubt this task is a challenge, so all opinions all welcome on this subject.

Thanks to all.