Nissan Almera

Hi the offside front suspension on my nissan almera is leaking fluid, and there is a knocking noise when driving which I have been told by a garage is the anti roll bar, is there a specific part of this it is likely to be, or does the whole thing require replacing? I have been quoted 150 - 200 ballpark figure (Pounds) Does this sound about right? Almera 1.4 97 62,000 miles