HI sooty

I replaced a few on mine a few years ago. It was no problem!! Take off the rocker cover, loosen the camshaft bearing caps (careful!!) and I had enough room to tilt the cam and change the loose ones.

But if its too tight then its better to remove the cam. Keep an eye on the chain that it doesnt fall.

as an aside, I wonder is your problem lifters? I had a clatter from my engine too and the lifters made no difference. Turned out compression was low on a few cylinders, bad gasket, and rough cyl bores. Trouble.
Anyway.......in the Haynes manual it shows how to check the lifters, push them down with a wooden rod and measure the clearance between lifter and cam lobe. I'm afraid I dont have Haynes man to hand for the clearances. make sure it is not on the lift portion of cam, otherwise no clearance. Do this before you take the cam bearings and timing chain off. As far as I remember you may have to remove the rad,fan, belt and some other bits to get at the crankshaft nut to turn the engine. See what you can get away with.

Good luck
Gerard