Our new template in Cars & Other Vehicles category is contrary to all appearrances very simple, especially for those who want to customize it by themselves.
The leading image is embedded as a module position "header" and in fact, if you would like to use this template for other thematic categories than Cars you just need to change the main picture. PSD sources attached to the purchased package will make it easy for you.
As to logo replacing, you just have to upload logo.png file to images in template directory.
I suggest taking a look at other template, which is similar in its simplicity to dj-car-company.
Let's see the dj-real-estate02 template. The principle of replacing the main image is the same as in dj-car-company. When it comes to background of grass which is extended to the entire page, you just need to change bg.jpg image to your own design or delete it if you don't need that.