Hi Bruce,
I recommend reading all the developer documents and watching/listening to all the training videos to get up to speed with both C#/ASP.NET and mojoPortal. I understand about the difficulty for visual impairment, while we do have quite a few developer docs besides the videos, unfortunately I can't say that we have equivalent non-video documentation for all of it. While you won't be able to get the full benefit, I still think the audio portion of the videos may help some. Ultimately the mojoPortal source code is the best documentation. By studying how mojoPortal features are implemented you can learn how to do things in your own custom features.
The first thing I want to point out to you is that it is a really bad idea to modify mojoPortal source code. Doing that means you will not be able to upgrade without losing your customizations. mojoPortal is actively developed and you will want to be able to upgrade to get new features and bug fixes. The main benefit of working with the source code is for learning and code examples of how to do things.
If you see the code that gets the data for a grid, you can right click the method in VS and choose "Go To Definition" and it will take you to that method. However as mentioned you should not modify the code to meet your needs. You should find ways to keep all of your custom code separate in your own projects without modifying any mojoPortal code. So for example if you want to show extra stuff on the memberlist, you should not modify th emember list that comes with mojoPortal nor any underlying code. You could create your own custom member list page and you can use a post build event in your custom project to copy your memberlist page up to the web project overwriting the one that is included. This way at least you are able to upgrade but you will need to restore your customizations after upgrading. For the extra data you want to display you should make your own table not modify the included tables, you can use the UserID or UserGuid to relate your custom table to users and make your own methods to lookup users and join your custom table.
http://www.mojoportal.com/avoid-forking-the-code.aspx
http://www.mojoportal.com/developerdocs.aspx
http://www.mojoportal.com/developertrainingvideos.aspx
Also if possible I recommend get the full version of Visual Studio 2010 instead of the Express version. You may qualify to get it free via the Web Site Spark program from Microsoft.
Hope it helps,
Joe