Hiya Michael,
The main problem you're having here is with the background image for the contentWrapper div.
I have attached a modified version of this - if you'd like to try it out.
If you want to try it out, rename the existing image 'contentWrapper_bg.jpg' in your siteassistpro_images folder to 'contentWrapper_bg_bak.jpg', and then put the attached image in the folder.
There are a couple of small adjustments I would make to the css (if it were me) but perhaps you could try this out first!
Cheers,