It's a good start but you need to work on the overall execution. My comments are in the image notes.

This isn't your logo. Make it a bit smaller.
This gradient is more distracting than anything
Good white space, but shrink it up to match a little bit better with the content.
Not quite sure why I would want to share my plan on facebook
Tabs only work if they are tabbing something. You should try dropping the rounded corners on top.
Plain forms are awesome, drop the fanciness.
Plain forms are awesome, drop the fanciness.
Make the footer stronger and the text line up. Also, there is such a difference between the first and second lines lengths. You should try making them more uniform. You could center it as well.
I like the simple interface. Two warnings however :
Well, you are right, it really need a lot of improvements. First of all get rid of these gradients, or at least change them. I also thik it would be better to replase blue color with red. And I really don't like buttons=). There are also some problems with fonts ( for example "Contact Seller").
There is something to be said about being minimal with design but there are good and bad ways to go about it.
I think with this design, you've gone too far over to the minimalist zone and not considered an approach which brings the user in to view the ad a little more closely.
In my view, a redesign of this page would include the following:
Make the image and thumbnail previews take up more space.
Condense the product information so it can be easily scanned by the visitor.
Put emphasis on the Contact form at the bottom of the page - make it more inviting for someone to fill it in and enquire about the ad.
Try throwing in some subtle use of the blue that you already have to displace the grey borders. The content area is too grey.
Rethink the labelling of your navigation - I wouldn't understand what 'get in' means if I was a new visitor - it's not obvious enough unless you look at the other navigation items.