It is very easy, remove the side cover from the right hand side of the engine block. Remove the valve cover and loosen the valve adjustment (on the faulty valve mechanism)slide the rocker back out of the way to remove the pushrod. Remove the faulty lifter from it's bore using a magnetic retrieving tool or rotate the engine by hand until the lifter moves up to it's highest point and grip it with a pair of channel locks or pliers and slide it out and discard it. NOTE: Generally all lifters wear at the same rate, my question is? why replace a single lifter? if they all wear at the same rate, they generally are replaced as a set.
By the way, there is an ONLINE FREE maintenance manual for the 216 engine which is the same procedure as a 235 engine for similar repairs, you can check out the specifics for lifter replacement there, also remember, when you replace lifters, you will have to readjust the valve tappet setting to the 235 specs. Here is the link to the online manual.
216 Online Manual
