urgent suffusion theme update issues – £10 paypal reward for most helpful!

My site is http://www.hh-bb.com

I’m not a wordpress master, everything’s been moved, the language is really confusing and I’m really lost!

My usual web guy whose shoulder I looked over when designing this is laid up with man flu and I have urgent updates to make…

Please help, a £10 paypal reward for the person who gives the simplest, most helpful ABC answers written in plain language. I created a thread earlier, and some replies had my head spinning..

1. I updated the wordpress theme to 3.3.1, suffusion theme to 3.9.6 and all my plugins yesterday, now ‘www.hh-bb.com loads ok’ but ‘hh-bb.com’ gives me this message:

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Server error
The website encountered an error while retrieving http://hh-bb.com/. It may be down for maintenance or configured incorrectly.
Here are some suggestions:
Reload this webpage later.
HTTP Error 500 (Internal Server Error): An unexpected condition was encountered while the server was attempting to fulfill the request.

****

2. The menu bar has moved up without permission – it should sit on that blue line below it.

3. All of my preview pics for each post have disappeared.

4. To top it off, the site is really, really sloooow. This is serious.

5. I can get to the dashboard and login area but when I click preview for any changes to a page, the new tab doesn’t display the preview, just this message:

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The website encountered an error while retrieving http://www.hh-bb.com/wp-admin/post.php. It may be down for maintenance or configured incorrectly.
Here are some suggestions:
Reload this webpage later.
HTTP Error 500 (Internal Server Error): An unexpected condition was encountered while the server was attempting to fulfill the request.

****

Even if I just click update, I get a blank white page.

Cheers