I doubt lifter replacement is simple. I have no first hand experience with any of this, just going by what i have read, so bear that in mind. I think that valve springs can be done with cams installed, but lifters, i believe the cams would need to come out - be a big job requiring some special tools and a work shop manual - definitely not for the faint of heart!
If it were me, i would do an oil and filter change and run the car for a few weeks - see if the noise settles down, if not, id try that Auto RX and possibly experiment with different oil brands / weights.
Google lifter noise and have a good read - seems very, very common and not too serious.
Next time Jamie97lsc has some heads in his shop, i will take a closer look at them - give me a better idea about our B heads heads and whats possible with the cams in place.
As i said in the PM, make ripping into the heads a last resort! Might be a 'can of worms' you wish you hadn't opened! Lol.