Their website is http://www.hamburger-dom.de/index2.html although I don't know if the attractions list is current; Olympia Looping's website isn't showing the dates for 2008 yet.
I believe Olympia Looping was 5 Euros or more per ride when we rode it last summer. Well worth it though.
The amount of time needed depends on what rides you're interested in and are willing to pay to ride. We only rode the coasters and the occasional giant Ferris wheel at the three German fairs we visited last summer. We spent more time walking around and sampling the food than riding but were probably at the fairs around 4 or 5 hours total.
CoasterKev!