any help

have a real issue here
all going well with WP site on zen server
then added plugin for back up;
May or may not be responsible or just coincidense.
then lost site as in cpanel all redirects were lost. So reset them all.
I then started in Chrome to get a malvirus alert when viewing the site. The dashboard was also distorted.
Some scripting was found inthe index file & the this was removed. for a while all was Ok and then noticed that it had rewritten the contamination script.
its gone from bad to worse ever since in that the dashboard cannot publish I just get a white screen and now I find that my old C5 site no longer exists except for the home page with a 404 error.
Google have attached a ‘don’t open this site can damage your PC’ to everything to do with my site.

At a complete loss to know what to do.
http://www.frenchhorseandcountry.com
http://www.frenchhorseandcountry.col/WP/
http://www.frenchhorseandcountry.com/C5/

Any help in any way very appreciated