Hi,
I'm not sure I understand your question. You can do pretty much anything with the Html Content feature, the links feature is a convenience but you can make links in an Html content instance and have more felxibility. If you know html well you can use source view and edit the markup directly.
If by shop you mean online ecommerce store, the WebStore feature is available but it currently only supports download products and is very basic.
The "release" packages of mojoPortal are pre-compiled, there is no C# source code, its already compiled into dll files in the bin folder.
If you want to work with the source code you have to download the source package and build it with VS 2008. However, I recomend that you don't change any code in mojoPortal as that will make it difficult or impossible for you to upgrade in the future. All customization should be done in external projects. If you make changes in mojoportal files you will lose them when you upgrade.
Hope it helps,
Joe