Hope everything has been well for you. For upgrading to V4 from V2.4.5, you will need to upgrade to V3 first, and then V4 in the future.. V2.4.5 is directly upgradable to V3.
To answer your question about customization: See this post: http://www.aspplayground....omization-m399461.aspx
With the theme and template system in place, we can change the look entirely. Take a look at our Mobile template (a drop down with theme selection at the top of the page) which is very simple and clean.