C5 2.2 ABS Modulator

[dawsy 22]

HI all my trusty 2001 2.2 C5 SX has thrown up a abs fault on plugging it in to my lexia it is reading permanent fault internal electro valve,would i be right in assuming this is inside the modulator and is not a service part,and I will kneed to change the whole unit,is this a straight forward job.I see on the lexia there is a brake bleed function I guess this is to remove any air from the modulator.Is there anybody on here who has changed a modulator who could give me some tips on how to carry out this process