I wonder if anyone on here can help clarify the process that needs to be followed here please?

Basically, my wifes car has had an engine warning light illuminated a few weeks back. Got a diagnostic test done on the message and it indicated 'camshaft sensor' fault and just needed replacing. It was safe to continue to drive I was told.

Last few days, car had appeared a little sluggish when starting up. Got it going each time and we put it down to the weather. Yesterday however, she would turn over but then cut out.

Got the camshaft sensor replaced but warning light still came back on. Was not with wife at the time. Apparently, the mechanic rang a nissan service bloke he knew, described the problem and said straight away, timing chains are gone. I was aware that there had been a historical fault on this model, but had hoped we had dodged a bullet with it, obviously not though.

Anyway, the mechanic is keen to help out but wants to establish, if the engine has to be removed completely to replace the chains or can he do the work with the engine in the car. Apparently having trouble getting back hold of this Nissan mechanic.

Can anyone clear up that matter for me? Will obviously make a massive difference on the labour costs, depending on the outcome. Whilst I am at it, does anyone know if in actual fact, after replacing the timing chains, is there any chance that there is actually something else wrong? Just worried about good money after bad. We have had some bad luck recently with this car. Its only a few months ago we had to replace the clutch and the gearbox (long story).

Any help or advice appreciated - thanks.