Agree with all the above. I had an '06 5 (flat top tube) from new and loved it. It never gave me a moments trouble and is now bringing a smile to my friend's face (giant-one). I changed it last year for a second hand '09 5AM that is also superb.
The Manitou shock gave good service but the Fox RP23 on my AM is noticably better. From memory the '07 was similar to the '06 except for the bent top tube. The angles slackened for '08 and went even slacker for '09.
Price depends on the spec. Rockshox would point towards the 'S' model. If this is the case it'll be worth a fair bit less then the Pro, AM or SE as the rest of the kit won't be top end. If it is a 2007 S I'd not want to pay more then about £700. I'd add another £100/200 to that if it's a higher spec.