how can i fix my vauxhall zafira 1.6 comfort?

my zafira keeps cutting out each time i slow down, the ecu light has been on but it goes out after a while, so i can't seem to find the problem without having to spend too much money on getting it diagnosed at the garage. Can anyone give me any ideas what may be cauing my car todo this? i have been told that the camshaft sensor may be blown but if it is this what will it cost to get this part supplied and fitted?