I have had a couple of CLK's and they have been very nice cars, no major problems with either of them. As mentioned though mercs of this vintage will likely have rust and it will be in the wheel arches and where the bumpers meets the wings front and back. The one you have posted up looks ok but could have been tarted up to sell and it will bubble back through if it has only been filled. Also the dash around the radio looks like it has been damaged - that would get annoying - and as for AMG edition the wheels are the only AMG thing on the car and I would have expected the full AMG bumpers and side skirts if this was a factory AMG, but otherwise it looks like it has a lot of options (full electric memory seats, parking sensors, command/sat nav, wooden steering wheel, digital climate control and heated seats) but a lot of money for a convertible merc that old in the middle of wnter with that mileage. I would have said it was worth £1800. The later shape CLK's are not a lot more (2002 onwards) and they are a much better car.
I hope that helps.
Darren.