Yes. To start, you need to download the source from codeplex.
I added a link to my post with the location to the Guest Book Source code.
You do not have to create a customized skin. You can use any existing skin.
I see you went from a page to form(s) so want more than one input form and now there's a product page.
Sounds like project scope creep is happening here. This appears to be bigger than you first mentioned
You can use the existing mojoPortal Store/Shopping cart module for a products page.
If you are doing multiple forms and are not an experienced developer, as Joe's said get his Form Wizard Pro.
Rick