I've done the 3.5 carb engine in my Range Rover, Long time ago but it was straightforward, nothing you couldnt do yourself. Just pay attention to the manual when re-fitting the valley gasket or you will get leaks.
But do you realy need a cam? Often the ticking noise is just worn followers, rockers and shafts, but then again, its half of the job done changing followers and you wouldnt want to be stripping it twice for the cam later.
I agree with the earlier post, change the cam chain at the same time, they are quite cheep.