with a high mileage 177k, no performance upgrades just a standard car with s/s exhaust, think the rattling at high revs 4-6krpm is to do with the cam lifters, followers have no idea about cams, what lifters are, what followers are and tappets are so please advise what i should replace this hydraulic cam with.

Not after super performance or anything, just the standard hydraulic alternative.

And can i do it myself?